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Diffstat (limited to 'src/runtime/mgc0.c')
| -rw-r--r-- | src/runtime/mgc0.c | 1918 |
1 files changed, 1918 insertions, 0 deletions
diff --git a/src/runtime/mgc0.c b/src/runtime/mgc0.c new file mode 100644 index 000000000..7ec9640eb --- /dev/null +++ b/src/runtime/mgc0.c @@ -0,0 +1,1918 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Garbage collector (GC). +// +// GC is: +// - mark&sweep +// - mostly precise (with the exception of some C-allocated objects, assembly frames/arguments, etc) +// - parallel (up to MaxGcproc threads) +// - partially concurrent (mark is stop-the-world, while sweep is concurrent) +// - non-moving/non-compacting +// - full (non-partial) +// +// GC rate. +// Next GC is after we've allocated an extra amount of memory proportional to +// the amount already in use. The proportion is controlled by GOGC environment variable +// (100 by default). If GOGC=100 and we're using 4M, we'll GC again when we get to 8M +// (this mark is tracked in next_gc variable). This keeps the GC cost in linear +// proportion to the allocation cost. Adjusting GOGC just changes the linear constant +// (and also the amount of extra memory used). +// +// Concurrent sweep. +// The sweep phase proceeds concurrently with normal program execution. +// The heap is swept span-by-span both lazily (when a goroutine needs another span) +// and concurrently in a background goroutine (this helps programs that are not CPU bound). +// However, at the end of the stop-the-world GC phase we don't know the size of the live heap, +// and so next_gc calculation is tricky and happens as follows. +// At the end of the stop-the-world phase next_gc is conservatively set based on total +// heap size; all spans are marked as "needs sweeping". +// Whenever a span is swept, next_gc is decremented by GOGC*newly_freed_memory. +// The background sweeper goroutine simply sweeps spans one-by-one bringing next_gc +// closer to the target value. However, this is not enough to avoid over-allocating memory. +// Consider that a goroutine wants to allocate a new span for a large object and +// there are no free swept spans, but there are small-object unswept spans. +// If the goroutine naively allocates a new span, it can surpass the yet-unknown +// target next_gc value. In order to prevent such cases (1) when a goroutine needs +// to allocate a new small-object span, it sweeps small-object spans for the same +// object size until it frees at least one object; (2) when a goroutine needs to +// allocate large-object span from heap, it sweeps spans until it frees at least +// that many pages into heap. Together these two measures ensure that we don't surpass +// target next_gc value by a large margin. There is an exception: if a goroutine sweeps +// and frees two nonadjacent one-page spans to the heap, it will allocate a new two-page span, +// but there can still be other one-page unswept spans which could be combined into a two-page span. +// It's critical to ensure that no operations proceed on unswept spans (that would corrupt +// mark bits in GC bitmap). During GC all mcaches are flushed into the central cache, +// so they are empty. When a goroutine grabs a new span into mcache, it sweeps it. +// When a goroutine explicitly frees an object or sets a finalizer, it ensures that +// the span is swept (either by sweeping it, or by waiting for the concurrent sweep to finish). +// The finalizer goroutine is kicked off only when all spans are swept. +// When the next GC starts, it sweeps all not-yet-swept spans (if any). + +#include "runtime.h" +#include "arch_GOARCH.h" +#include "malloc.h" +#include "stack.h" +#include "mgc0.h" +#include "chan.h" +#include "race.h" +#include "type.h" +#include "typekind.h" +#include "funcdata.h" +#include "textflag.h" + +enum { + Debug = 0, + ConcurrentSweep = 0, + PreciseScan = 1, + + WorkbufSize = 4*1024, + FinBlockSize = 4*1024, + RootData = 0, + RootBss = 1, + RootFinalizers = 2, + RootSpans = 3, + RootFlushCaches = 4, + RootCount = 5, + +#ifdef _64BIT + byteEndian = BigEndian*7, +#else + byteEndian = BigEndian*3, +#endif +}; + +#define ScanConservatively ((byte*)1) + +// Initialized from $GOGC. GOGC=off means no gc. +extern int32 runtime·gcpercent; + +// Holding worldsema grants an M the right to try to stop the world. +// The procedure is: +// +// runtime·semacquire(&runtime·worldsema); +// m->gcing = 1; +// runtime·stoptheworld(); +// +// ... do stuff ... +// +// m->gcing = 0; +// runtime·semrelease(&runtime·worldsema); +// runtime·starttheworld(); +// +uint32 runtime·worldsema = 1; + +typedef struct Workbuf Workbuf; +struct Workbuf +{ + LFNode node; // must be first + uintptr nobj; + byte* obj[(WorkbufSize-sizeof(LFNode)-sizeof(uintptr))/PtrSize]; +}; + +extern byte runtime·data[]; +extern byte runtime·edata[]; +extern byte runtime·bss[]; +extern byte runtime·ebss[]; + +extern byte runtime·gcdata[]; +extern byte runtime·gcbss[]; + +Mutex runtime·finlock; // protects the following variables +G* runtime·fing; // goroutine that runs finalizers +FinBlock* runtime·finq; // list of finalizers that are to be executed +FinBlock* runtime·finc; // cache of free blocks +bool runtime·fingwait; +bool runtime·fingwake; +static FinBlock *allfin; // list of all blocks + +BitVector runtime·gcdatamask; +BitVector runtime·gcbssmask; + +static Mutex gclock; + +static void bgsweep(void); +static Workbuf* getempty(Workbuf*); +static Workbuf* getfull(Workbuf*); +static void putempty(Workbuf*); +static Workbuf* handoff(Workbuf*); +static void gchelperstart(void); +static void flushallmcaches(void); +static bool scanframe(Stkframe *frame, void *unused); +static void scanstack(G *gp); +static BitVector unrollglobgcprog(byte *prog, uintptr size); + +static FuncVal bgsweepv = {bgsweep}; + +static struct { + uint64 full; // lock-free list of full blocks + uint64 empty; // lock-free list of empty blocks + byte pad0[CacheLineSize]; // prevents false-sharing between full/empty and nproc/nwait + uint32 nproc; + int64 tstart; + volatile uint32 nwait; + volatile uint32 ndone; + Note alldone; + ParFor* markfor; + + // Copy of mheap.allspans for marker or sweeper. + MSpan** spans; + uint32 nspan; +} work; + +// scanblock scans a block of n bytes starting at pointer b for references +// to other objects, scanning any it finds recursively until there are no +// unscanned objects left. Instead of using an explicit recursion, it keeps +// a work list in the Workbuf* structures and loops in the main function +// body. Keeping an explicit work list is easier on the stack allocator and +// more efficient. +static void +scanblock(byte *b, uintptr n, byte *ptrmask) +{ + byte *obj, *p, *arena_start, *arena_used, **wp, *scanbuf[8], *ptrbitp, *bitp, bits, xbits, shift, cached; + uintptr i, nobj, size, idx, x, off, scanbufpos; + intptr ncached; + Workbuf *wbuf; + Iface *iface; + Eface *eface; + Type *typ; + MSpan *s; + pageID k; + bool keepworking; + + // Cache memory arena parameters in local vars. + arena_start = runtime·mheap.arena_start; + arena_used = runtime·mheap.arena_used; + + wbuf = getempty(nil); + nobj = wbuf->nobj; + wp = &wbuf->obj[nobj]; + keepworking = b == nil; + scanbufpos = 0; + for(i = 0; i < nelem(scanbuf); i++) + scanbuf[i] = nil; + + ptrbitp = nil; + cached = 0; + ncached = 0; + + // ptrmask can have 3 possible values: + // 1. nil - obtain pointer mask from GC bitmap. + // 2. ScanConservatively - don't use any mask, scan conservatively. + // 3. pointer to a compact mask (for stacks and data). + if(b != nil) + goto scanobj; + for(;;) { + if(nobj == 0) { + // Out of work in workbuf. + // First, see is there is any work in scanbuf. + for(i = 0; i < nelem(scanbuf); i++) { + b = scanbuf[scanbufpos]; + scanbuf[scanbufpos++] = nil; + if(scanbufpos == nelem(scanbuf)) + scanbufpos = 0; + if(b != nil) { + n = arena_used - b; // scan until bitBoundary or BitsDead + ptrmask = nil; // use GC bitmap for pointer info + goto scanobj; + } + } + if(!keepworking) { + putempty(wbuf); + return; + } + // Refill workbuf from global queue. + wbuf = getfull(wbuf); + if(wbuf == nil) + return; + nobj = wbuf->nobj; + wp = &wbuf->obj[nobj]; + } + + // If another proc wants a pointer, give it some. + if(work.nwait > 0 && nobj > 4 && work.full == 0) { + wbuf->nobj = nobj; + wbuf = handoff(wbuf); + nobj = wbuf->nobj; + wp = &wbuf->obj[nobj]; + } + + wp--; + nobj--; + b = *wp; + n = arena_used - b; // scan until next bitBoundary or BitsDead + ptrmask = nil; // use GC bitmap for pointer info + + scanobj: + if(!PreciseScan) { + if(ptrmask == nil) { + // Heap obj, obtain real size. + if(!runtime·mlookup(b, &p, &n, nil)) + continue; // not an allocated obj + if(b != p) + runtime·throw("bad heap object"); + } + ptrmask = ScanConservatively; + } + // Find bits of the beginning of the object. + if(ptrmask == nil) { + off = (uintptr*)b - (uintptr*)arena_start; + ptrbitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + cached = *ptrbitp >> shift; + cached &= ~bitBoundary; + ncached = (8 - shift)/gcBits; + } + for(i = 0; i < n; i += PtrSize) { + obj = nil; + // Find bits for this word. + if(ptrmask == nil) { + // Check is we have reached end of span. + if((((uintptr)b+i)%PageSize) == 0 && + runtime·mheap.spans[(b-arena_start)>>PageShift] != runtime·mheap.spans[(b+i-arena_start)>>PageShift]) + break; + // Consult GC bitmap. + if(ncached <= 0) { + // Refill cache. + cached = *--ptrbitp; + ncached = 2; + } + bits = cached; + cached >>= gcBits; + ncached--; + if((bits&bitBoundary) != 0) + break; // reached beginning of the next object + bits = (bits>>2)&BitsMask; + if(bits == BitsDead) + break; // reached no-scan part of the object + } else if(ptrmask != ScanConservatively) // dense mask (stack or data) + bits = (ptrmask[(i/PtrSize)/4]>>(((i/PtrSize)%4)*BitsPerPointer))&BitsMask; + else + bits = BitsPointer; + + if(bits == BitsScalar || bits == BitsDead) + continue; + if(bits == BitsPointer) { + obj = *(byte**)(b+i); + goto markobj; + } + + // With those three out of the way, must be multi-word. + if(bits != BitsMultiWord) + runtime·throw("unexpected garbage collection bits"); + // Find the next pair of bits. + if(ptrmask == nil) { + if(ncached <= 0) { + // Refill cache. + cached = *--ptrbitp; + ncached = 2; + } + bits = (cached>>2)&BitsMask; + } else + bits = (ptrmask[((i+PtrSize)/PtrSize)/4]>>((((i+PtrSize)/PtrSize)%4)*BitsPerPointer))&BitsMask; + + switch(bits) { + default: + runtime·throw("unexpected garbage collection bits"); + case BitsIface: + iface = (Iface*)(b+i); + if(iface->tab != nil) { + typ = iface->tab->type; + if(!(typ->kind&KindDirectIface) || !(typ->kind&KindNoPointers)) + obj = iface->data; + } + break; + case BitsEface: + eface = (Eface*)(b+i); + typ = eface->type; + if(typ != nil) { + if(!(typ->kind&KindDirectIface) || !(typ->kind&KindNoPointers)) + obj = eface->data; + } + break; + } + + i += PtrSize; + cached >>= gcBits; + ncached--; + + markobj: + // At this point we have extracted the next potential pointer. + // Check if it points into heap. + if(obj == nil || obj < arena_start || obj >= arena_used) + continue; + // Mark the object. + off = (uintptr*)obj - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + xbits = *bitp; + bits = (xbits >> shift) & bitMask; + if((bits&bitBoundary) == 0) { + // Not a beginning of a block, consult span table to find the block beginning. + k = (uintptr)obj>>PageShift; + x = k; + x -= (uintptr)arena_start>>PageShift; + s = runtime·mheap.spans[x]; + if(s == nil || k < s->start || obj >= s->limit || s->state != MSpanInUse) + continue; + p = (byte*)((uintptr)s->start<<PageShift); + if(s->sizeclass != 0) { + size = s->elemsize; + idx = ((byte*)obj - p)/size; + p = p+idx*size; + } + if(p == obj) { + runtime·printf("runtime: failed to find block beginning for %p s=%p s->limit=%p\n", + p, s->start*PageSize, s->limit); + runtime·throw("failed to find block beginning"); + } + obj = p; + goto markobj; + } + + // Now we have bits, bitp, and shift correct for + // obj pointing at the base of the object. + // Only care about not marked objects. + if((bits&bitMarked) != 0) + continue; + // If obj size is greater than 8, then each byte of GC bitmap + // contains info for at most one object. In such case we use + // non-atomic byte store to mark the object. This can lead + // to double enqueue of the object for scanning, but scanning + // is an idempotent operation, so it is OK. This cannot lead + // to bitmap corruption because the single marked bit is the + // only thing that can change in the byte. + // For 8-byte objects we use non-atomic store, if the other + // quadruple is already marked. Otherwise we resort to CAS + // loop for marking. + if((xbits&(bitMask|(bitMask<<gcBits))) != (bitBoundary|(bitBoundary<<gcBits)) || + work.nproc == 1) + *bitp = xbits | (bitMarked<<shift); + else + runtime·atomicor8(bitp, bitMarked<<shift); + + if(((xbits>>(shift+2))&BitsMask) == BitsDead) + continue; // noscan object + + // Queue the obj for scanning. + PREFETCH(obj); + obj = (byte*)((uintptr)obj & ~(PtrSize-1)); + p = scanbuf[scanbufpos]; + scanbuf[scanbufpos++] = obj; + if(scanbufpos == nelem(scanbuf)) + scanbufpos = 0; + if(p == nil) + continue; + + // If workbuf is full, obtain an empty one. + if(nobj >= nelem(wbuf->obj)) { + wbuf->nobj = nobj; + wbuf = getempty(wbuf); + nobj = wbuf->nobj; + wp = &wbuf->obj[nobj]; + } + *wp = p; + wp++; + nobj++; + } + + if(Debug && ptrmask == nil) { + // For heap objects ensure that we did not overscan. + n = 0; + p = nil; + if(!runtime·mlookup(b, &p, &n, nil) || b != p || i > n) { + runtime·printf("runtime: scanned (%p,%p), heap object (%p,%p)\n", b, i, p, n); + runtime·throw("scanblock: scanned invalid object"); + } + } + } +} + +static void +markroot(ParFor *desc, uint32 i) +{ + FinBlock *fb; + MSpan *s; + uint32 spanidx, sg; + G *gp; + void *p; + uint32 status; + bool restart; + + USED(&desc); + // Note: if you add a case here, please also update heapdump.c:dumproots. + switch(i) { + case RootData: + scanblock(runtime·data, runtime·edata - runtime·data, runtime·gcdatamask.bytedata); + break; + + case RootBss: + scanblock(runtime·bss, runtime·ebss - runtime·bss, runtime·gcbssmask.bytedata); + break; + + case RootFinalizers: + for(fb=allfin; fb; fb=fb->alllink) + scanblock((byte*)fb->fin, fb->cnt*sizeof(fb->fin[0]), ScanConservatively); + break; + + case RootSpans: + // mark MSpan.specials + sg = runtime·mheap.sweepgen; + for(spanidx=0; spanidx<work.nspan; spanidx++) { + Special *sp; + SpecialFinalizer *spf; + + s = work.spans[spanidx]; + if(s->state != MSpanInUse) + continue; + if(s->sweepgen != sg) { + runtime·printf("sweep %d %d\n", s->sweepgen, sg); + runtime·throw("gc: unswept span"); + } + for(sp = s->specials; sp != nil; sp = sp->next) { + if(sp->kind != KindSpecialFinalizer) + continue; + // don't mark finalized object, but scan it so we + // retain everything it points to. + spf = (SpecialFinalizer*)sp; + // A finalizer can be set for an inner byte of an object, find object beginning. + p = (void*)((s->start << PageShift) + spf->special.offset/s->elemsize*s->elemsize); + scanblock(p, s->elemsize, nil); + scanblock((void*)&spf->fn, PtrSize, ScanConservatively); + } + } + break; + + case RootFlushCaches: + flushallmcaches(); + break; + + default: + // the rest is scanning goroutine stacks + if(i - RootCount >= runtime·allglen) + runtime·throw("markroot: bad index"); + gp = runtime·allg[i - RootCount]; + // remember when we've first observed the G blocked + // needed only to output in traceback + status = runtime·readgstatus(gp); + if((status == Gwaiting || status == Gsyscall) && gp->waitsince == 0) + gp->waitsince = work.tstart; + // Shrink a stack if not much of it is being used. + runtime·shrinkstack(gp); + if(runtime·readgstatus(gp) == Gdead) + gp->gcworkdone = true; + else + gp->gcworkdone = false; + restart = runtime·stopg(gp); + scanstack(gp); + if(restart) + runtime·restartg(gp); + break; + } +} + +// Get an empty work buffer off the work.empty list, +// allocating new buffers as needed. +static Workbuf* +getempty(Workbuf *b) +{ + MCache *c; + + if(b != nil) + runtime·lfstackpush(&work.full, &b->node); + b = nil; + c = g->m->mcache; + if(c->gcworkbuf != nil) { + b = c->gcworkbuf; + c->gcworkbuf = nil; + } + if(b == nil) + b = (Workbuf*)runtime·lfstackpop(&work.empty); + if(b == nil) + b = runtime·persistentalloc(sizeof(*b), CacheLineSize, &mstats.gc_sys); + b->nobj = 0; + return b; +} + +static void +putempty(Workbuf *b) +{ + MCache *c; + + c = g->m->mcache; + if(c->gcworkbuf == nil) { + c->gcworkbuf = b; + return; + } + runtime·lfstackpush(&work.empty, &b->node); +} + +void +runtime·gcworkbuffree(void *b) +{ + if(b != nil) + putempty(b); +} + +// Get a full work buffer off the work.full list, or return nil. +static Workbuf* +getfull(Workbuf *b) +{ + int32 i; + + if(b != nil) + runtime·lfstackpush(&work.empty, &b->node); + b = (Workbuf*)runtime·lfstackpop(&work.full); + if(b != nil || work.nproc == 1) + return b; + + runtime·xadd(&work.nwait, +1); + for(i=0;; i++) { + if(work.full != 0) { + runtime·xadd(&work.nwait, -1); + b = (Workbuf*)runtime·lfstackpop(&work.full); + if(b != nil) + return b; + runtime·xadd(&work.nwait, +1); + } + if(work.nwait == work.nproc) + return nil; + if(i < 10) { + g->m->gcstats.nprocyield++; + runtime·procyield(20); + } else if(i < 20) { + g->m->gcstats.nosyield++; + runtime·osyield(); + } else { + g->m->gcstats.nsleep++; + runtime·usleep(100); + } + } +} + +static Workbuf* +handoff(Workbuf *b) +{ + int32 n; + Workbuf *b1; + + // Make new buffer with half of b's pointers. + b1 = getempty(nil); + n = b->nobj/2; + b->nobj -= n; + b1->nobj = n; + runtime·memmove(b1->obj, b->obj+b->nobj, n*sizeof b1->obj[0]); + g->m->gcstats.nhandoff++; + g->m->gcstats.nhandoffcnt += n; + + // Put b on full list - let first half of b get stolen. + runtime·lfstackpush(&work.full, &b->node); + return b1; +} + +BitVector +runtime·stackmapdata(StackMap *stackmap, int32 n) +{ + if(n < 0 || n >= stackmap->n) + runtime·throw("stackmapdata: index out of range"); + return (BitVector){stackmap->nbit, stackmap->bytedata + 4*n*((stackmap->nbit+31)/32)}; +} + +// Scan a stack frame: local variables and function arguments/results. +static bool +scanframe(Stkframe *frame, void *unused) +{ + Func *f; + StackMap *stackmap; + BitVector bv; + uintptr size; + uintptr targetpc; + int32 pcdata; + + USED(unused); + f = frame->fn; + targetpc = frame->continpc; + if(targetpc == 0) { + // Frame is dead. + return true; + } + if(Debug > 1) + runtime·printf("scanframe %s\n", runtime·funcname(f)); + if(targetpc != f->entry) + targetpc--; + pcdata = runtime·pcdatavalue(f, PCDATA_StackMapIndex, targetpc); + if(pcdata == -1) { + // We do not have a valid pcdata value but there might be a + // stackmap for this function. It is likely that we are looking + // at the function prologue, assume so and hope for the best. + pcdata = 0; + } + + // Scan local variables if stack frame has been allocated. + // Use pointer information if known. + stackmap = runtime·funcdata(f, FUNCDATA_LocalsPointerMaps); + if(stackmap == nil) { + // No locals information, scan everything. + size = frame->varp - frame->sp; + if(Debug > 2) + runtime·printf("frame %s unsized locals %p+%p\n", runtime·funcname(f), (byte*)(frame->varp-size), size); + scanblock((byte*)(frame->varp - size), size, ScanConservatively); + } else if(stackmap->n < 0) { + // Locals size information, scan just the locals. + size = -stackmap->n; + if(Debug > 2) + runtime·printf("frame %s conservative locals %p+%p\n", runtime·funcname(f), (byte*)(frame->varp-size), size); + scanblock((byte*)(frame->varp - size), size, ScanConservatively); + } else if(stackmap->n > 0) { + // Locals bitmap information, scan just the pointers in locals. + if(pcdata < 0 || pcdata >= stackmap->n) { + // don't know where we are + runtime·printf("pcdata is %d and %d stack map entries for %s (targetpc=%p)\n", + pcdata, stackmap->n, runtime·funcname(f), targetpc); + runtime·throw("scanframe: bad symbol table"); + } + bv = runtime·stackmapdata(stackmap, pcdata); + size = (bv.n * PtrSize) / BitsPerPointer; + scanblock((byte*)frame->varp - size, bv.n/BitsPerPointer*PtrSize, (byte*)bv.bytedata); + } + + // Scan arguments. + // Use pointer information if known. + stackmap = runtime·funcdata(f, FUNCDATA_ArgsPointerMaps); + if(stackmap != nil) { + bv = runtime·stackmapdata(stackmap, pcdata); + scanblock((byte*)frame->argp, bv.n/BitsPerPointer*PtrSize, (byte*)bv.bytedata); + } else { + if(Debug > 2) + runtime·printf("frame %s conservative args %p+%p\n", runtime·funcname(f), frame->argp, (uintptr)frame->arglen); + scanblock((byte*)frame->argp, frame->arglen, ScanConservatively); + } + return true; +} + +static void +scanstack(G *gp) +{ + M *mp; + int32 n; + Stktop *stk; + uintptr sp, guard; + bool (*fn)(Stkframe*, void*); + + if(runtime·readgstatus(gp)&Gscan == 0) { + runtime·printf("runtime: gp=%p, goid=%D, gp->atomicstatus=%d\n", gp, gp->goid, runtime·readgstatus(gp)); + runtime·throw("mark - bad status"); + } + + switch(runtime·readgstatus(gp)&~Gscan) { + default: + runtime·printf("runtime: gp=%p, goid=%D, gp->atomicstatus=%d\n", gp, gp->goid, runtime·readgstatus(gp)); + runtime·throw("mark - bad status"); + case Gdead: + return; + case Grunning: + runtime·printf("runtime: gp=%p, goid=%D, gp->atomicstatus=%d\n", gp, gp->goid, runtime·readgstatus(gp)); + runtime·throw("mark - world not stopped"); + case Grunnable: + case Gsyscall: + case Gwaiting: + break; + } + + if(gp == g) + runtime·throw("can't scan our own stack"); + if((mp = gp->m) != nil && mp->helpgc) + runtime·throw("can't scan gchelper stack"); + + if(gp->syscallstack != (uintptr)nil) { + // Scanning another goroutine that is about to enter or might + // have just exited a system call. It may be executing code such + // as schedlock and may have needed to start a new stack segment. + // Use the stack segment and stack pointer at the time of + // the system call instead, since that won't change underfoot. + sp = gp->syscallsp; + stk = (Stktop*)gp->syscallstack; + guard = gp->syscallguard; + } else { + // Scanning another goroutine's stack. + // The goroutine is usually asleep (the world is stopped). + sp = gp->sched.sp; + stk = (Stktop*)gp->stackbase; + guard = gp->stackguard; + } + if(ScanStackByFrames) { + USED(sp); + USED(stk); + USED(guard); + fn = scanframe; + runtime·gentraceback(~(uintptr)0, ~(uintptr)0, 0, gp, 0, nil, 0x7fffffff, &fn, nil, false); + } else { + n = 0; + while(stk) { + if(sp < guard-StackGuard || (uintptr)stk < sp) { + runtime·printf("scanstack inconsistent: g%D#%d sp=%p not in [%p,%p]\n", gp->goid, n, sp, guard-StackGuard, stk); + runtime·throw("scanstack"); + } + if(Debug > 2) + runtime·printf("conservative stack %p+%p\n", (byte*)sp, (uintptr)stk-sp); + scanblock((byte*)sp, (uintptr)stk - sp, ScanConservatively); + sp = stk->gobuf.sp; + guard = stk->stackguard; + stk = (Stktop*)stk->stackbase; + n++; + } + } +} + +// The gp has been moved to a gc safepoint. If there is gcphase specific +// work it is done here. +void +runtime·gcphasework(G *gp) +{ + switch(runtime·gcphase) { + default: + runtime·throw("gcphasework in bad gcphase"); + case GCoff: + case GCquiesce: + case GCstw: + case GCsweep: + // No work for now. + break; + case GCmark: + // Disabled until concurrent GC is implemented + // but indicate the scan has been done. + // scanstack(gp); + break; + } + gp->gcworkdone = true; +} + +void +runtime·queuefinalizer(byte *p, FuncVal *fn, uintptr nret, Type *fint, PtrType *ot) +{ + FinBlock *block; + Finalizer *f; + + runtime·lock(&runtime·finlock); + if(runtime·finq == nil || runtime·finq->cnt == runtime·finq->cap) { + if(runtime·finc == nil) { + runtime·finc = runtime·persistentalloc(FinBlockSize, 0, &mstats.gc_sys); + runtime·finc->cap = (FinBlockSize - sizeof(FinBlock)) / sizeof(Finalizer) + 1; + runtime·finc->alllink = allfin; + allfin = runtime·finc; + } + block = runtime·finc; + runtime·finc = block->next; + block->next = runtime·finq; + runtime·finq = block; + } + f = &runtime·finq->fin[runtime·finq->cnt]; + runtime·finq->cnt++; + f->fn = fn; + f->nret = nret; + f->fint = fint; + f->ot = ot; + f->arg = p; + runtime·fingwake = true; + runtime·unlock(&runtime·finlock); +} + +void +runtime·iterate_finq(void (*callback)(FuncVal*, byte*, uintptr, Type*, PtrType*)) +{ + FinBlock *fb; + Finalizer *f; + uintptr i; + + for(fb = allfin; fb; fb = fb->alllink) { + for(i = 0; i < fb->cnt; i++) { + f = &fb->fin[i]; + callback(f->fn, f->arg, f->nret, f->fint, f->ot); + } + } +} + +void +runtime·MSpan_EnsureSwept(MSpan *s) +{ + uint32 sg; + + // Caller must disable preemption. + // Otherwise when this function returns the span can become unswept again + // (if GC is triggered on another goroutine). + if(g->m->locks == 0 && g->m->mallocing == 0 && g != g->m->g0) + runtime·throw("MSpan_EnsureSwept: m is not locked"); + + sg = runtime·mheap.sweepgen; + if(runtime·atomicload(&s->sweepgen) == sg) + return; + if(runtime·cas(&s->sweepgen, sg-2, sg-1)) { + runtime·MSpan_Sweep(s, false); + return; + } + // unfortunate condition, and we don't have efficient means to wait + while(runtime·atomicload(&s->sweepgen) != sg) + runtime·osyield(); +} + +// Sweep frees or collects finalizers for blocks not marked in the mark phase. +// It clears the mark bits in preparation for the next GC round. +// Returns true if the span was returned to heap. +// If preserve=true, don't return it to heap nor relink in MCentral lists; +// caller takes care of it. +bool +runtime·MSpan_Sweep(MSpan *s, bool preserve) +{ + int32 cl, n, npages, nfree; + uintptr size, off, step; + uint32 sweepgen; + byte *p, *bitp, shift, xbits, bits; + MCache *c; + byte *arena_start; + MLink head, *end, *link; + Special *special, **specialp, *y; + bool res, sweepgenset; + + // It's critical that we enter this function with preemption disabled, + // GC must not start while we are in the middle of this function. + if(g->m->locks == 0 && g->m->mallocing == 0 && g != g->m->g0) + runtime·throw("MSpan_Sweep: m is not locked"); + sweepgen = runtime·mheap.sweepgen; + if(s->state != MSpanInUse || s->sweepgen != sweepgen-1) { + runtime·printf("MSpan_Sweep: state=%d sweepgen=%d mheap.sweepgen=%d\n", + s->state, s->sweepgen, sweepgen); + runtime·throw("MSpan_Sweep: bad span state"); + } + arena_start = runtime·mheap.arena_start; + cl = s->sizeclass; + size = s->elemsize; + if(cl == 0) { + n = 1; + } else { + // Chunk full of small blocks. + npages = runtime·class_to_allocnpages[cl]; + n = (npages << PageShift) / size; + } + res = false; + nfree = 0; + end = &head; + c = g->m->mcache; + sweepgenset = false; + + // Mark any free objects in this span so we don't collect them. + for(link = s->freelist; link != nil; link = link->next) { + off = (uintptr*)link - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + *bitp |= bitMarked<<shift; + } + + // Unlink & free special records for any objects we're about to free. + specialp = &s->specials; + special = *specialp; + while(special != nil) { + // A finalizer can be set for an inner byte of an object, find object beginning. + p = (byte*)(s->start << PageShift) + special->offset/size*size; + off = (uintptr*)p - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + bits = (*bitp>>shift) & bitMask; + if((bits&bitMarked) == 0) { + // Find the exact byte for which the special was setup + // (as opposed to object beginning). + p = (byte*)(s->start << PageShift) + special->offset; + // about to free object: splice out special record + y = special; + special = special->next; + *specialp = special; + if(!runtime·freespecial(y, p, size, false)) { + // stop freeing of object if it has a finalizer + *bitp |= bitMarked << shift; + } + } else { + // object is still live: keep special record + specialp = &special->next; + special = *specialp; + } + } + + // Sweep through n objects of given size starting at p. + // This thread owns the span now, so it can manipulate + // the block bitmap without atomic operations. + p = (byte*)(s->start << PageShift); + // Find bits for the beginning of the span. + off = (uintptr*)p - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = 0; + step = size/(PtrSize*wordsPerBitmapByte); + // Rewind to the previous quadruple as we move to the next + // in the beginning of the loop. + bitp += step; + if(step == 0) { + // 8-byte objects. + bitp++; + shift = gcBits; + } + for(; n > 0; n--, p += size) { + bitp -= step; + if(step == 0) { + if(shift != 0) + bitp--; + shift = gcBits - shift; + } + + xbits = *bitp; + bits = (xbits>>shift) & bitMask; + + // Allocated and marked object, reset bits to allocated. + if((bits&bitMarked) != 0) { + *bitp &= ~(bitMarked<<shift); + continue; + } + // At this point we know that we are looking at garbage object + // that needs to be collected. + if(runtime·debug.allocfreetrace) + runtime·tracefree(p, size); + // Reset to allocated+noscan. + *bitp = (xbits & ~((bitMarked|(BitsMask<<2))<<shift)) | ((uintptr)BitsDead<<(shift+2)); + if(cl == 0) { + // Free large span. + if(preserve) + runtime·throw("can't preserve large span"); + runtime·unmarkspan(p, s->npages<<PageShift); + s->needzero = 1; + // important to set sweepgen before returning it to heap + runtime·atomicstore(&s->sweepgen, sweepgen); + sweepgenset = true; + // NOTE(rsc,dvyukov): The original implementation of efence + // in CL 22060046 used SysFree instead of SysFault, so that + // the operating system would eventually give the memory + // back to us again, so that an efence program could run + // longer without running out of memory. Unfortunately, + // calling SysFree here without any kind of adjustment of the + // heap data structures means that when the memory does + // come back to us, we have the wrong metadata for it, either in + // the MSpan structures or in the garbage collection bitmap. + // Using SysFault here means that the program will run out of + // memory fairly quickly in efence mode, but at least it won't + // have mysterious crashes due to confused memory reuse. + // It should be possible to switch back to SysFree if we also + // implement and then call some kind of MHeap_DeleteSpan. + if(runtime·debug.efence) { + s->limit = nil; // prevent mlookup from finding this span + runtime·SysFault(p, size); + } else + runtime·MHeap_Free(&runtime·mheap, s, 1); + c->local_nlargefree++; + c->local_largefree += size; + runtime·xadd64(&mstats.next_gc, -(uint64)(size * (runtime·gcpercent + 100)/100)); + res = true; + } else { + // Free small object. + if(size > 2*sizeof(uintptr)) + ((uintptr*)p)[1] = (uintptr)0xdeaddeaddeaddeadll; // mark as "needs to be zeroed" + else if(size > sizeof(uintptr)) + ((uintptr*)p)[1] = 0; + + end->next = (MLink*)p; + end = (MLink*)p; + nfree++; + } + } + + // We need to set s->sweepgen = h->sweepgen only when all blocks are swept, + // because of the potential for a concurrent free/SetFinalizer. + // But we need to set it before we make the span available for allocation + // (return it to heap or mcentral), because allocation code assumes that a + // span is already swept if available for allocation. + + if(!sweepgenset && nfree == 0) { + // The span must be in our exclusive ownership until we update sweepgen, + // check for potential races. + if(s->state != MSpanInUse || s->sweepgen != sweepgen-1) { + runtime·printf("MSpan_Sweep: state=%d sweepgen=%d mheap.sweepgen=%d\n", + s->state, s->sweepgen, sweepgen); + runtime·throw("MSpan_Sweep: bad span state after sweep"); + } + runtime·atomicstore(&s->sweepgen, sweepgen); + } + if(nfree > 0) { + c->local_nsmallfree[cl] += nfree; + c->local_cachealloc -= nfree * size; + runtime·xadd64(&mstats.next_gc, -(uint64)(nfree * size * (runtime·gcpercent + 100)/100)); + res = runtime·MCentral_FreeSpan(&runtime·mheap.central[cl].mcentral, s, nfree, head.next, end, preserve); + // MCentral_FreeSpan updates sweepgen + } + return res; +} + +// State of background sweep. +// Pretected by gclock. +static struct +{ + G* g; + bool parked; + + uint32 spanidx; // background sweeper position + + uint32 nbgsweep; + uint32 npausesweep; +} sweep; + +// background sweeping goroutine +static void +bgsweep(void) +{ + g->issystem = true; + for(;;) { + while(runtime·sweepone() != -1) { + sweep.nbgsweep++; + runtime·gosched(); + } + runtime·lock(&gclock); + if(!runtime·mheap.sweepdone) { + // It's possible if GC has happened between sweepone has + // returned -1 and gclock lock. + runtime·unlock(&gclock); + continue; + } + sweep.parked = true; + runtime·parkunlock(&gclock, runtime·gostringnocopy((byte*)"GC sweep wait")); + } +} + +// sweeps one span +// returns number of pages returned to heap, or -1 if there is nothing to sweep +uintptr +runtime·sweepone(void) +{ + MSpan *s; + uint32 idx, sg; + uintptr npages; + + // increment locks to ensure that the goroutine is not preempted + // in the middle of sweep thus leaving the span in an inconsistent state for next GC + g->m->locks++; + sg = runtime·mheap.sweepgen; + for(;;) { + idx = runtime·xadd(&sweep.spanidx, 1) - 1; + if(idx >= work.nspan) { + runtime·mheap.sweepdone = true; + g->m->locks--; + return -1; + } + s = work.spans[idx]; + if(s->state != MSpanInUse) { + s->sweepgen = sg; + continue; + } + if(s->sweepgen != sg-2 || !runtime·cas(&s->sweepgen, sg-2, sg-1)) + continue; + npages = s->npages; + if(!runtime·MSpan_Sweep(s, false)) + npages = 0; + g->m->locks--; + return npages; + } +} + +void +runtime·gchelper(void) +{ + uint32 nproc; + + g->m->traceback = 2; + gchelperstart(); + + // parallel mark for over gc roots + runtime·parfordo(work.markfor); + + // help other threads scan secondary blocks + scanblock(nil, 0, nil); + + nproc = work.nproc; // work.nproc can change right after we increment work.ndone + if(runtime·xadd(&work.ndone, +1) == nproc-1) + runtime·notewakeup(&work.alldone); + g->m->traceback = 0; +} + +static void +cachestats(void) +{ + MCache *c; + P *p, **pp; + + for(pp=runtime·allp; p=*pp; pp++) { + c = p->mcache; + if(c==nil) + continue; + runtime·purgecachedstats(c); + } +} + +static void +flushallmcaches(void) +{ + P *p, **pp; + MCache *c; + + // Flush MCache's to MCentral. + for(pp=runtime·allp; p=*pp; pp++) { + c = p->mcache; + if(c==nil) + continue; + runtime·MCache_ReleaseAll(c); + runtime·stackcache_clear(c); + } +} + +static void +flushallmcaches_m(G *gp) +{ + flushallmcaches(); + runtime·gogo(&gp->sched); +} + +void +runtime·updatememstats(GCStats *stats) +{ + M *mp; + MSpan *s; + int32 i; + uint64 smallfree; + uint64 *src, *dst; + void (*fn)(G*); + + if(stats) + runtime·memclr((byte*)stats, sizeof(*stats)); + for(mp=runtime·allm; mp; mp=mp->alllink) { + if(stats) { + src = (uint64*)&mp->gcstats; + dst = (uint64*)stats; + for(i=0; i<sizeof(*stats)/sizeof(uint64); i++) + dst[i] += src[i]; + runtime·memclr((byte*)&mp->gcstats, sizeof(mp->gcstats)); + } + } + mstats.mcache_inuse = runtime·mheap.cachealloc.inuse; + mstats.mspan_inuse = runtime·mheap.spanalloc.inuse; + mstats.sys = mstats.heap_sys + mstats.stacks_sys + mstats.mspan_sys + + mstats.mcache_sys + mstats.buckhash_sys + mstats.gc_sys + mstats.other_sys; + + // Calculate memory allocator stats. + // During program execution we only count number of frees and amount of freed memory. + // Current number of alive object in the heap and amount of alive heap memory + // are calculated by scanning all spans. + // Total number of mallocs is calculated as number of frees plus number of alive objects. + // Similarly, total amount of allocated memory is calculated as amount of freed memory + // plus amount of alive heap memory. + mstats.alloc = 0; + mstats.total_alloc = 0; + mstats.nmalloc = 0; + mstats.nfree = 0; + for(i = 0; i < nelem(mstats.by_size); i++) { + mstats.by_size[i].nmalloc = 0; + mstats.by_size[i].nfree = 0; + } + + // Flush MCache's to MCentral. + if(g == g->m->g0) + flushallmcaches(); + else { + fn = flushallmcaches_m; + runtime·mcall(&fn); + } + + // Aggregate local stats. + cachestats(); + + // Scan all spans and count number of alive objects. + runtime·lock(&runtime·mheap.lock); + for(i = 0; i < runtime·mheap.nspan; i++) { + s = runtime·mheap.allspans[i]; + if(s->state != MSpanInUse) + continue; + if(s->sizeclass == 0) { + mstats.nmalloc++; + mstats.alloc += s->elemsize; + } else { + mstats.nmalloc += s->ref; + mstats.by_size[s->sizeclass].nmalloc += s->ref; + mstats.alloc += s->ref*s->elemsize; + } + } + runtime·unlock(&runtime·mheap.lock); + + // Aggregate by size class. + smallfree = 0; + mstats.nfree = runtime·mheap.nlargefree; + for(i = 0; i < nelem(mstats.by_size); i++) { + mstats.nfree += runtime·mheap.nsmallfree[i]; + mstats.by_size[i].nfree = runtime·mheap.nsmallfree[i]; + mstats.by_size[i].nmalloc += runtime·mheap.nsmallfree[i]; + smallfree += runtime·mheap.nsmallfree[i] * runtime·class_to_size[i]; + } + mstats.nmalloc += mstats.nfree; + + // Calculate derived stats. + mstats.total_alloc = mstats.alloc + runtime·mheap.largefree + smallfree; + mstats.heap_alloc = mstats.alloc; + mstats.heap_objects = mstats.nmalloc - mstats.nfree; +} + +// Structure of arguments passed to function gc(). +// This allows the arguments to be passed via runtime·mcall. +struct gc_args +{ + int64 start_time; // start time of GC in ns (just before stoptheworld) + bool eagersweep; +}; + +static void gc(struct gc_args *args); +static void mgc(G *gp); + +int32 +runtime·readgogc(void) +{ + byte *p; + + p = runtime·getenv("GOGC"); + if(p == nil || p[0] == '\0') + return 100; + if(runtime·strcmp(p, (byte*)"off") == 0) + return -1; + return runtime·atoi(p); +} + +void +runtime·gcinit(void) +{ + if(sizeof(Workbuf) != WorkbufSize) + runtime·throw("runtime: size of Workbuf is suboptimal"); + + work.markfor = runtime·parforalloc(MaxGcproc); + runtime·gcpercent = runtime·readgogc(); + runtime·gcdatamask = unrollglobgcprog(runtime·gcdata, runtime·edata - runtime·data); + runtime·gcbssmask = unrollglobgcprog(runtime·gcbss, runtime·ebss - runtime·bss); +} + +void +runtime·gc_m(void) +{ + struct gc_args a; + G *gp; + + gp = g->m->curg; + runtime·casgstatus(gp, Grunning, Gwaiting); + gp->waitreason = runtime·gostringnocopy((byte*)"garbage collection"); + + a.start_time = (uint64)(g->m->scalararg[0]) | ((uint64)(g->m->scalararg[1]) << 32); + a.eagersweep = g->m->scalararg[2]; + gc(&a); + + runtime·casgstatus(gp, Gwaiting, Grunning); +} + +static void +gc(struct gc_args *args) +{ + int64 t0, t1, t2, t3, t4; + uint64 heap0, heap1, obj; + GCStats stats; + + if(runtime·debug.allocfreetrace) + runtime·tracegc(); + + g->m->traceback = 2; + t0 = args->start_time; + work.tstart = args->start_time; + + t1 = 0; + if(runtime·debug.gctrace) + t1 = runtime·nanotime(); + + // Sweep what is not sweeped by bgsweep. + while(runtime·sweepone() != -1) + sweep.npausesweep++; + + // Cache runtime.mheap.allspans in work.spans to avoid conflicts with + // resizing/freeing allspans. + // New spans can be created while GC progresses, but they are not garbage for + // this round: + // - new stack spans can be created even while the world is stopped. + // - new malloc spans can be created during the concurrent sweep + + // Even if this is stop-the-world, a concurrent exitsyscall can allocate a stack from heap. + runtime·lock(&runtime·mheap.lock); + // Free the old cached sweep array if necessary. + if(work.spans != nil && work.spans != runtime·mheap.allspans) + runtime·SysFree(work.spans, work.nspan*sizeof(work.spans[0]), &mstats.other_sys); + // Cache the current array for marking. + runtime·mheap.gcspans = runtime·mheap.allspans; + work.spans = runtime·mheap.allspans; + work.nspan = runtime·mheap.nspan; + runtime·unlock(&runtime·mheap.lock); + + work.nwait = 0; + work.ndone = 0; + work.nproc = runtime·gcprocs(); + runtime·parforsetup(work.markfor, work.nproc, RootCount + runtime·allglen, nil, false, markroot); + if(work.nproc > 1) { + runtime·noteclear(&work.alldone); + runtime·helpgc(work.nproc); + } + + t2 = 0; + if(runtime·debug.gctrace) + t2 = runtime·nanotime(); + + gchelperstart(); + runtime·parfordo(work.markfor); + scanblock(nil, 0, nil); + + t3 = 0; + if(runtime·debug.gctrace) + t3 = runtime·nanotime(); + + if(work.nproc > 1) + runtime·notesleep(&work.alldone); + + cachestats(); + // next_gc calculation is tricky with concurrent sweep since we don't know size of live heap + // estimate what was live heap size after previous GC (for tracing only) + heap0 = mstats.next_gc*100/(runtime·gcpercent+100); + // conservatively set next_gc to high value assuming that everything is live + // concurrent/lazy sweep will reduce this number while discovering new garbage + mstats.next_gc = mstats.heap_alloc+mstats.heap_alloc*runtime·gcpercent/100; + + t4 = runtime·nanotime(); + runtime·atomicstore64(&mstats.last_gc, runtime·unixnanotime()); // must be Unix time to make sense to user + mstats.pause_ns[mstats.numgc%nelem(mstats.pause_ns)] = t4 - t0; + mstats.pause_total_ns += t4 - t0; + mstats.numgc++; + if(mstats.debuggc) + runtime·printf("pause %D\n", t4-t0); + + if(runtime·debug.gctrace) { + heap1 = mstats.heap_alloc; + runtime·updatememstats(&stats); + if(heap1 != mstats.heap_alloc) { + runtime·printf("runtime: mstats skew: heap=%D/%D\n", heap1, mstats.heap_alloc); + runtime·throw("mstats skew"); + } + obj = mstats.nmalloc - mstats.nfree; + + stats.nprocyield += work.markfor->nprocyield; + stats.nosyield += work.markfor->nosyield; + stats.nsleep += work.markfor->nsleep; + + runtime·printf("gc%d(%d): %D+%D+%D+%D us, %D -> %D MB, %D (%D-%D) objects," + " %d/%d/%d sweeps," + " %D(%D) handoff, %D(%D) steal, %D/%D/%D yields\n", + mstats.numgc, work.nproc, (t1-t0)/1000, (t2-t1)/1000, (t3-t2)/1000, (t4-t3)/1000, + heap0>>20, heap1>>20, obj, + mstats.nmalloc, mstats.nfree, + work.nspan, sweep.nbgsweep, sweep.npausesweep, + stats.nhandoff, stats.nhandoffcnt, + work.markfor->nsteal, work.markfor->nstealcnt, + stats.nprocyield, stats.nosyield, stats.nsleep); + sweep.nbgsweep = sweep.npausesweep = 0; + } + + // See the comment in the beginning of this function as to why we need the following. + // Even if this is still stop-the-world, a concurrent exitsyscall can allocate a stack from heap. + runtime·lock(&runtime·mheap.lock); + // Free the old cached mark array if necessary. + if(work.spans != nil && work.spans != runtime·mheap.allspans) + runtime·SysFree(work.spans, work.nspan*sizeof(work.spans[0]), &mstats.other_sys); + // Cache the current array for sweeping. + runtime·mheap.gcspans = runtime·mheap.allspans; + runtime·mheap.sweepgen += 2; + runtime·mheap.sweepdone = false; + work.spans = runtime·mheap.allspans; + work.nspan = runtime·mheap.nspan; + sweep.spanidx = 0; + runtime·unlock(&runtime·mheap.lock); + + // Temporary disable concurrent sweep, because we see failures on builders. + if(ConcurrentSweep && !args->eagersweep) { + runtime·lock(&gclock); + if(sweep.g == nil) + sweep.g = runtime·newproc1(&bgsweepv, nil, 0, 0, gc); + else if(sweep.parked) { + sweep.parked = false; + runtime·ready(sweep.g); + } + runtime·unlock(&gclock); + } else { + // Sweep all spans eagerly. + while(runtime·sweepone() != -1) + sweep.npausesweep++; + } + + runtime·mProf_GC(); + g->m->traceback = 0; +} + +extern uintptr runtime·sizeof_C_MStats; + +void +runtime·ReadMemStats(MStats *stats) +{ + // Have to acquire worldsema to stop the world, + // because stoptheworld can only be used by + // one goroutine at a time, and there might be + // a pending garbage collection already calling it. + runtime·semacquire(&runtime·worldsema, false); + g->m->gcing = 1; + runtime·stoptheworld(); + runtime·updatememstats(nil); + // Size of the trailing by_size array differs between Go and C, + // NumSizeClasses was changed, but we can not change Go struct because of backward compatibility. + runtime·memmove(stats, &mstats, runtime·sizeof_C_MStats); + + // Stack numbers are part of the heap numbers, separate those out for user consumption + stats->stacks_sys = stats->stacks_inuse; + stats->heap_inuse -= stats->stacks_inuse; + stats->heap_sys -= stats->stacks_inuse; + + g->m->gcing = 0; + g->m->locks++; + runtime·semrelease(&runtime·worldsema); + runtime·starttheworld(); + g->m->locks--; +} + +void +runtime∕debug·readGCStats(Slice *pauses) +{ + uint64 *p; + uint32 i, n; + + // Calling code in runtime/debug should make the slice large enough. + if(pauses->cap < nelem(mstats.pause_ns)+3) + runtime·throw("runtime: short slice passed to readGCStats"); + + // Pass back: pauses, last gc (absolute time), number of gc, total pause ns. + p = (uint64*)pauses->array; + runtime·lock(&runtime·mheap.lock); + n = mstats.numgc; + if(n > nelem(mstats.pause_ns)) + n = nelem(mstats.pause_ns); + + // The pause buffer is circular. The most recent pause is at + // pause_ns[(numgc-1)%nelem(pause_ns)], and then backward + // from there to go back farther in time. We deliver the times + // most recent first (in p[0]). + for(i=0; i<n; i++) + p[i] = mstats.pause_ns[(mstats.numgc-1-i)%nelem(mstats.pause_ns)]; + + p[n] = mstats.last_gc; + p[n+1] = mstats.numgc; + p[n+2] = mstats.pause_total_ns; + runtime·unlock(&runtime·mheap.lock); + pauses->len = n+3; +} + +void +runtime·setgcpercent_m(void) { + int32 in; + int32 out; + + in = (int32)(intptr)g->m->scalararg[0]; + + runtime·lock(&runtime·mheap.lock); + out = runtime·gcpercent; + if(in < 0) + in = -1; + runtime·gcpercent = in; + runtime·unlock(&runtime·mheap.lock); + + g->m->scalararg[0] = (uintptr)(intptr)out; +} + +static void +gchelperstart(void) +{ + if(g->m->helpgc < 0 || g->m->helpgc >= MaxGcproc) + runtime·throw("gchelperstart: bad m->helpgc"); + if(g != g->m->g0) + runtime·throw("gchelper not running on g0 stack"); +} + +G* +runtime·wakefing(void) +{ + G *res; + + res = nil; + runtime·lock(&runtime·finlock); + if(runtime·fingwait && runtime·fingwake) { + runtime·fingwait = false; + runtime·fingwake = false; + res = runtime·fing; + } + runtime·unlock(&runtime·finlock); + return res; +} + +// Recursively unrolls GC program in prog. +// mask is where to store the result. +// ppos is a pointer to position in mask, in bits. +// sparse says to generate 4-bits per word mask for heap (2-bits for data/bss otherwise). +static byte* +unrollgcprog1(byte *mask, byte *prog, uintptr *ppos, bool inplace, bool sparse) +{ + uintptr pos, siz, i, off; + byte *arena_start, *prog1, v, *bitp, shift; + + arena_start = runtime·mheap.arena_start; + pos = *ppos; + for(;;) { + switch(prog[0]) { + case insData: + prog++; + siz = prog[0]; + prog++; + for(i = 0; i < siz; i++) { + v = prog[i/PointersPerByte]; + v >>= (i%PointersPerByte)*BitsPerPointer; + v &= BitsMask; + if(inplace) { + // Store directly into GC bitmap. + off = (uintptr*)(mask+pos) - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + if(shift==0) + *bitp = 0; + *bitp |= v<<(shift+2); + pos += PtrSize; + } else if(sparse) { + // 4-bits per word + v <<= (pos%8)+2; + mask[pos/8] |= v; + pos += gcBits; + } else { + // 2-bits per word + v <<= pos%8; + mask[pos/8] |= v; + pos += BitsPerPointer; + } + } + prog += ROUND(siz*BitsPerPointer, 8)/8; + break; + case insArray: + prog++; + siz = 0; + for(i = 0; i < PtrSize; i++) + siz = (siz<<8) + prog[PtrSize-i-1]; + prog += PtrSize; + prog1 = nil; + for(i = 0; i < siz; i++) + prog1 = unrollgcprog1(mask, prog, &pos, inplace, sparse); + if(prog1[0] != insArrayEnd) + runtime·throw("unrollgcprog: array does not end with insArrayEnd"); + prog = prog1+1; + break; + case insArrayEnd: + case insEnd: + *ppos = pos; + return prog; + default: + runtime·throw("unrollgcprog: unknown instruction"); + } + } +} + +// Unrolls GC program prog for data/bss, returns dense GC mask. +static BitVector +unrollglobgcprog(byte *prog, uintptr size) +{ + byte *mask; + uintptr pos, masksize; + + masksize = ROUND(ROUND(size, PtrSize)/PtrSize*BitsPerPointer, 8)/8; + mask = runtime·persistentalloc(masksize+1, 0, &mstats.gc_sys); + mask[masksize] = 0xa1; + pos = 0; + prog = unrollgcprog1(mask, prog, &pos, false, false); + if(pos != size/PtrSize*BitsPerPointer) { + runtime·printf("unrollglobgcprog: bad program size, got %D, expect %D\n", + (uint64)pos, (uint64)size/PtrSize*BitsPerPointer); + runtime·throw("unrollglobgcprog: bad program size"); + } + if(prog[0] != insEnd) + runtime·throw("unrollglobgcprog: program does not end with insEnd"); + if(mask[masksize] != 0xa1) + runtime·throw("unrollglobgcprog: overflow"); + return (BitVector){masksize*8, mask}; +} + +void +runtime·unrollgcproginplace_m(void) +{ + uintptr size, size0, pos, off; + byte *arena_start, *prog, *bitp, shift; + Type *typ; + void *v; + + v = g->m->ptrarg[0]; + typ = g->m->ptrarg[1]; + size = g->m->scalararg[0]; + size0 = g->m->scalararg[1]; + g->m->ptrarg[0] = nil; + g->m->ptrarg[1] = nil; + + pos = 0; + prog = (byte*)typ->gc[1]; + while(pos != size0) + unrollgcprog1(v, prog, &pos, true, true); + // Mark first word as bitAllocated. + arena_start = runtime·mheap.arena_start; + off = (uintptr*)v - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + *bitp |= bitBoundary<<shift; + // Mark word after last as BitsDead. + if(size0 < size) { + off = (uintptr*)((byte*)v + size0) - (uintptr*)arena_start; + bitp = arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + *bitp &= ~(bitPtrMask<<shift) | ((uintptr)BitsDead<<(shift+2)); + } +} + +// Unrolls GC program in typ->gc[1] into typ->gc[0] +void +runtime·unrollgcprog_m(void) +{ + static Mutex lock; + Type *typ; + byte *mask, *prog; + uintptr pos; + uintptr x; + + typ = g->m->ptrarg[0]; + g->m->ptrarg[0] = nil; + + runtime·lock(&lock); + mask = (byte*)typ->gc[0]; + if(mask[0] == 0) { + pos = 8; // skip the unroll flag + prog = (byte*)typ->gc[1]; + prog = unrollgcprog1(mask, prog, &pos, false, true); + if(prog[0] != insEnd) + runtime·throw("unrollgcprog: program does not end with insEnd"); + if(((typ->size/PtrSize)%2) != 0) { + // repeat the program twice + prog = (byte*)typ->gc[1]; + unrollgcprog1(mask, prog, &pos, false, true); + } + + // atomic way to say mask[0] = 1 + x = typ->gc[0]; + ((byte*)&x)[0] = 1; + runtime·atomicstorep((void**)mask, (void*)x); + } + runtime·unlock(&lock); +} + +// mark the span of memory at v as having n blocks of the given size. +// if leftover is true, there is left over space at the end of the span. +void +runtime·markspan(void *v, uintptr size, uintptr n, bool leftover) +{ + uintptr i, off, step; + byte *b; + + if((byte*)v+size*n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start) + runtime·throw("markspan: bad pointer"); + + // Find bits of the beginning of the span. + off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start; // word offset + b = runtime·mheap.arena_start - off/wordsPerBitmapByte - 1; + if((off%wordsPerBitmapByte) != 0) + runtime·throw("markspan: unaligned length"); + + // Okay to use non-atomic ops here, because we control + // the entire span, and each bitmap byte has bits for only + // one span, so no other goroutines are changing these bitmap words. + + if(size == PtrSize) { + // Possible only on 64-bits (minimal size class is 8 bytes). + // Poor man's memset(0x11). + if(0x11 != ((bitBoundary+BitsDead)<<gcBits) + (bitBoundary+BitsDead)) + runtime·throw("markspan: bad bits"); + if((n%(wordsPerBitmapByte*PtrSize)) != 0) + runtime·throw("markspan: unaligned length"); + b = b - n/wordsPerBitmapByte + 1; // find first byte + if(((uintptr)b%PtrSize) != 0) + runtime·throw("markspan: unaligned pointer"); + for(i = 0; i != n; i += wordsPerBitmapByte*PtrSize, b += PtrSize) + *(uintptr*)b = (uintptr)0x1111111111111111ULL; // bitBoundary+BitsDead + return; + } + + if(leftover) + n++; // mark a boundary just past end of last block too + step = size/(PtrSize*wordsPerBitmapByte); + for(i = 0; i != n; i++, b -= step) + *b = bitBoundary|(BitsDead<<2); +} + +// unmark the span of memory at v of length n bytes. +void +runtime·unmarkspan(void *v, uintptr n) +{ + uintptr off; + byte *b; + + if((byte*)v+n > (byte*)runtime·mheap.arena_used || (byte*)v < runtime·mheap.arena_start) + runtime·throw("markspan: bad pointer"); + + off = (uintptr*)v - (uintptr*)runtime·mheap.arena_start; // word offset + if((off % (PtrSize*wordsPerBitmapByte)) != 0) + runtime·throw("markspan: unaligned pointer"); + b = runtime·mheap.arena_start - off/wordsPerBitmapByte - 1; + n /= PtrSize; + if(n%(PtrSize*wordsPerBitmapByte) != 0) + runtime·throw("unmarkspan: unaligned length"); + // Okay to use non-atomic ops here, because we control + // the entire span, and each bitmap word has bits for only + // one span, so no other goroutines are changing these + // bitmap words. + n /= wordsPerBitmapByte; + runtime·memclr(b - n + 1, n); +} + +void +runtime·MHeap_MapBits(MHeap *h) +{ + // Caller has added extra mappings to the arena. + // Add extra mappings of bitmap words as needed. + // We allocate extra bitmap pieces in chunks of bitmapChunk. + enum { + bitmapChunk = 8192 + }; + uintptr n; + + n = (h->arena_used - h->arena_start) / (PtrSize*wordsPerBitmapByte); + n = ROUND(n, bitmapChunk); + n = ROUND(n, PhysPageSize); + if(h->bitmap_mapped >= n) + return; + + runtime·SysMap(h->arena_start - n, n - h->bitmap_mapped, h->arena_reserved, &mstats.gc_sys); + h->bitmap_mapped = n; +} + +static bool +getgcmaskcb(Stkframe *frame, void *ctxt) +{ + Stkframe *frame0; + + frame0 = ctxt; + if(frame->sp <= frame0->sp && frame0->sp < frame->varp) { + *frame0 = *frame; + return false; + } + return true; +} + +// Returns GC type info for object p for testing. +void +runtime·getgcmask(byte *p, Type *t, byte **mask, uintptr *len) +{ + Stkframe frame; + uintptr i, n, off; + byte *base, bits, shift, *b; + bool (*cb)(Stkframe*, void*); + + *mask = nil; + *len = 0; + + // data + if(p >= runtime·data && p < runtime·edata) { + n = ((PtrType*)t)->elem->size; + *len = n/PtrSize; + *mask = runtime·mallocgc(*len, nil, 0); + for(i = 0; i < n; i += PtrSize) { + off = (p+i-runtime·data)/PtrSize; + bits = (runtime·gcdatamask.bytedata[off/PointersPerByte] >> ((off%PointersPerByte)*BitsPerPointer))&BitsMask; + (*mask)[i/PtrSize] = bits; + } + return; + } + // bss + if(p >= runtime·bss && p < runtime·ebss) { + n = ((PtrType*)t)->elem->size; + *len = n/PtrSize; + *mask = runtime·mallocgc(*len, nil, 0); + for(i = 0; i < n; i += PtrSize) { + off = (p+i-runtime·bss)/PtrSize; + bits = (runtime·gcbssmask.bytedata[off/PointersPerByte] >> ((off%PointersPerByte)*BitsPerPointer))&BitsMask; + (*mask)[i/PtrSize] = bits; + } + return; + } + // heap + if(runtime·mlookup(p, &base, &n, nil)) { + *len = n/PtrSize; + *mask = runtime·mallocgc(*len, nil, 0); + for(i = 0; i < n; i += PtrSize) { + off = (uintptr*)(base+i) - (uintptr*)runtime·mheap.arena_start; + b = runtime·mheap.arena_start - off/wordsPerBitmapByte - 1; + shift = (off % wordsPerBitmapByte) * gcBits; + bits = (*b >> (shift+2))&BitsMask; + (*mask)[i/PtrSize] = bits; + } + return; + } + // stack + frame.fn = nil; + frame.sp = (uintptr)p; + cb = getgcmaskcb; + runtime·gentraceback(g->m->curg->sched.pc, g->m->curg->sched.sp, 0, g->m->curg, 0, nil, 1000, &cb, &frame, false); + if(frame.fn != nil) { + Func *f; + StackMap *stackmap; + BitVector bv; + uintptr size; + uintptr targetpc; + int32 pcdata; + + f = frame.fn; + targetpc = frame.continpc; + if(targetpc == 0) + return; + if(targetpc != f->entry) + targetpc--; + pcdata = runtime·pcdatavalue(f, PCDATA_StackMapIndex, targetpc); + if(pcdata == -1) + return; + stackmap = runtime·funcdata(f, FUNCDATA_LocalsPointerMaps); + if(stackmap == nil || stackmap->n <= 0) + return; + bv = runtime·stackmapdata(stackmap, pcdata); + size = bv.n/BitsPerPointer*PtrSize; + n = ((PtrType*)t)->elem->size; + *len = n/PtrSize; + *mask = runtime·mallocgc(*len, nil, 0); + for(i = 0; i < n; i += PtrSize) { + off = (p+i-(byte*)frame.varp+size)/PtrSize; + bits = (bv.bytedata[off/PointersPerByte] >> ((off%PointersPerByte)*BitsPerPointer))&BitsMask; + (*mask)[i/PtrSize] = bits; + } + } +} + +void runtime·gc_unixnanotime(int64 *now); + +int64 runtime·unixnanotime(void) +{ + int64 now; + + runtime·gc_unixnanotime(&now); + return now; +} |