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Diffstat (limited to 'src/pkg/runtime/cpuprof.go')
| -rw-r--r-- | src/pkg/runtime/cpuprof.go | 425 |
1 files changed, 0 insertions, 425 deletions
diff --git a/src/pkg/runtime/cpuprof.go b/src/pkg/runtime/cpuprof.go deleted file mode 100644 index 8b1c1c632..000000000 --- a/src/pkg/runtime/cpuprof.go +++ /dev/null @@ -1,425 +0,0 @@ -// Copyright 2011 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. - -// CPU profiling. -// Based on algorithms and data structures used in -// http://code.google.com/p/google-perftools/. -// -// The main difference between this code and the google-perftools -// code is that this code is written to allow copying the profile data -// to an arbitrary io.Writer, while the google-perftools code always -// writes to an operating system file. -// -// The signal handler for the profiling clock tick adds a new stack trace -// to a hash table tracking counts for recent traces. Most clock ticks -// hit in the cache. In the event of a cache miss, an entry must be -// evicted from the hash table, copied to a log that will eventually be -// written as profile data. The google-perftools code flushed the -// log itself during the signal handler. This code cannot do that, because -// the io.Writer might block or need system calls or locks that are not -// safe to use from within the signal handler. Instead, we split the log -// into two halves and let the signal handler fill one half while a goroutine -// is writing out the other half. When the signal handler fills its half, it -// offers to swap with the goroutine. If the writer is not done with its half, -// we lose the stack trace for this clock tick (and record that loss). -// The goroutine interacts with the signal handler by calling getprofile() to -// get the next log piece to write, implicitly handing back the last log -// piece it obtained. -// -// The state of this dance between the signal handler and the goroutine -// is encoded in the Profile.handoff field. If handoff == 0, then the goroutine -// is not using either log half and is waiting (or will soon be waiting) for -// a new piece by calling notesleep(&p->wait). If the signal handler -// changes handoff from 0 to non-zero, it must call notewakeup(&p->wait) -// to wake the goroutine. The value indicates the number of entries in the -// log half being handed off. The goroutine leaves the non-zero value in -// place until it has finished processing the log half and then flips the number -// back to zero. Setting the high bit in handoff means that the profiling is over, -// and the goroutine is now in charge of flushing the data left in the hash table -// to the log and returning that data. -// -// The handoff field is manipulated using atomic operations. -// For the most part, the manipulation of handoff is orderly: if handoff == 0 -// then the signal handler owns it and can change it to non-zero. -// If handoff != 0 then the goroutine owns it and can change it to zero. -// If that were the end of the story then we would not need to manipulate -// handoff using atomic operations. The operations are needed, however, -// in order to let the log closer set the high bit to indicate "EOF" safely -// in the situation when normally the goroutine "owns" handoff. - -package runtime - -import "unsafe" - -const ( - numBuckets = 1 << 10 - logSize = 1 << 17 - assoc = 4 - maxCPUProfStack = 64 -) - -type cpuprofEntry struct { - count uintptr - depth uintptr - stack [maxCPUProfStack]uintptr -} - -type cpuProfile struct { - on bool // profiling is on - wait note // goroutine waits here - count uintptr // tick count - evicts uintptr // eviction count - lost uintptr // lost ticks that need to be logged - - // Active recent stack traces. - hash [numBuckets]struct { - entry [assoc]cpuprofEntry - } - - // Log of traces evicted from hash. - // Signal handler has filled log[toggle][:nlog]. - // Goroutine is writing log[1-toggle][:handoff]. - log [2][logSize / 2]uintptr - nlog uintptr - toggle int32 - handoff uint32 - - // Writer state. - // Writer maintains its own toggle to avoid races - // looking at signal handler's toggle. - wtoggle uint32 - wholding bool // holding & need to release a log half - flushing bool // flushing hash table - profile is over - eodSent bool // special end-of-data record sent; => flushing -} - -var ( - cpuprofLock mutex - cpuprof *cpuProfile - - eod = [3]uintptr{0, 1, 0} -) - -func setcpuprofilerate_m() // proc.c - -func setcpuprofilerate(hz int32) { - g := getg() - g.m.scalararg[0] = uintptr(hz) - onM(setcpuprofilerate_m) -} - -// lostProfileData is a no-op function used in profiles -// to mark the number of profiling stack traces that were -// discarded due to slow data writers. -func lostProfileData() {} - -// SetCPUProfileRate sets the CPU profiling rate to hz samples per second. -// If hz <= 0, SetCPUProfileRate turns off profiling. -// If the profiler is on, the rate cannot be changed without first turning it off. -// -// Most clients should use the runtime/pprof package or -// the testing package's -test.cpuprofile flag instead of calling -// SetCPUProfileRate directly. -func SetCPUProfileRate(hz int) { - // Clamp hz to something reasonable. - if hz < 0 { - hz = 0 - } - if hz > 1000000 { - hz = 1000000 - } - - lock(&cpuprofLock) - if hz > 0 { - if cpuprof == nil { - cpuprof = (*cpuProfile)(sysAlloc(unsafe.Sizeof(cpuProfile{}), &memstats.other_sys)) - if cpuprof == nil { - print("runtime: cpu profiling cannot allocate memory\n") - unlock(&cpuprofLock) - return - } - } - if cpuprof.on || cpuprof.handoff != 0 { - print("runtime: cannot set cpu profile rate until previous profile has finished.\n") - unlock(&cpuprofLock) - return - } - - cpuprof.on = true - // pprof binary header format. - // http://code.google.com/p/google-perftools/source/browse/trunk/src/profiledata.cc#117 - p := &cpuprof.log[0] - p[0] = 0 // count for header - p[1] = 3 // depth for header - p[2] = 0 // version number - p[3] = uintptr(1e6 / hz) // period (microseconds) - p[4] = 0 - cpuprof.nlog = 5 - cpuprof.toggle = 0 - cpuprof.wholding = false - cpuprof.wtoggle = 0 - cpuprof.flushing = false - cpuprof.eodSent = false - noteclear(&cpuprof.wait) - - setcpuprofilerate(int32(hz)) - } else if cpuprof != nil && cpuprof.on { - setcpuprofilerate(0) - cpuprof.on = false - - // Now add is not running anymore, and getprofile owns the entire log. - // Set the high bit in prof->handoff to tell getprofile. - for { - n := cpuprof.handoff - if n&0x80000000 != 0 { - print("runtime: setcpuprofile(off) twice\n") - } - if cas(&cpuprof.handoff, n, n|0x80000000) { - if n == 0 { - // we did the transition from 0 -> nonzero so we wake getprofile - notewakeup(&cpuprof.wait) - } - break - } - } - } - unlock(&cpuprofLock) -} - -func cpuproftick(pc *uintptr, n int32) { - if n > maxCPUProfStack { - n = maxCPUProfStack - } - s := (*[maxCPUProfStack]uintptr)(unsafe.Pointer(pc))[:n] - cpuprof.add(s) -} - -// add adds the stack trace to the profile. -// It is called from signal handlers and other limited environments -// and cannot allocate memory or acquire locks that might be -// held at the time of the signal, nor can it use substantial amounts -// of stack. It is allowed to call evict. -func (p *cpuProfile) add(pc []uintptr) { - // Compute hash. - h := uintptr(0) - for _, x := range pc { - h = h<<8 | (h >> (8 * (unsafe.Sizeof(h) - 1))) - h += x*31 + x*7 + x*3 - } - p.count++ - - // Add to entry count if already present in table. - b := &p.hash[h%numBuckets] -Assoc: - for i := range b.entry { - e := &b.entry[i] - if e.depth != uintptr(len(pc)) { - continue - } - for j := range pc { - if e.stack[j] != pc[j] { - continue Assoc - } - } - e.count++ - return - } - - // Evict entry with smallest count. - var e *cpuprofEntry - for i := range b.entry { - if e == nil || b.entry[i].count < e.count { - e = &b.entry[i] - } - } - if e.count > 0 { - if !p.evict(e) { - // Could not evict entry. Record lost stack. - p.lost++ - return - } - p.evicts++ - } - - // Reuse the newly evicted entry. - e.depth = uintptr(len(pc)) - e.count = 1 - copy(e.stack[:], pc) -} - -// evict copies the given entry's data into the log, so that -// the entry can be reused. evict is called from add, which -// is called from the profiling signal handler, so it must not -// allocate memory or block. It is safe to call flushlog. -// evict returns true if the entry was copied to the log, -// false if there was no room available. -func (p *cpuProfile) evict(e *cpuprofEntry) bool { - d := e.depth - nslot := d + 2 - log := &p.log[p.toggle] - if p.nlog+nslot > uintptr(len(p.log[0])) { - if !p.flushlog() { - return false - } - log = &p.log[p.toggle] - } - - q := p.nlog - log[q] = e.count - q++ - log[q] = d - q++ - copy(log[q:], e.stack[:d]) - q += d - p.nlog = q - e.count = 0 - return true -} - -// flushlog tries to flush the current log and switch to the other one. -// flushlog is called from evict, called from add, called from the signal handler, -// so it cannot allocate memory or block. It can try to swap logs with -// the writing goroutine, as explained in the comment at the top of this file. -func (p *cpuProfile) flushlog() bool { - if !cas(&p.handoff, 0, uint32(p.nlog)) { - return false - } - notewakeup(&p.wait) - - p.toggle = 1 - p.toggle - log := &p.log[p.toggle] - q := uintptr(0) - if p.lost > 0 { - lostPC := funcPC(lostProfileData) - log[0] = p.lost - log[1] = 1 - log[2] = lostPC - q = 3 - p.lost = 0 - } - p.nlog = q - return true -} - -// getprofile blocks until the next block of profiling data is available -// and returns it as a []byte. It is called from the writing goroutine. -func (p *cpuProfile) getprofile() []byte { - if p == nil { - return nil - } - - if p.wholding { - // Release previous log to signal handling side. - // Loop because we are racing against SetCPUProfileRate(0). - for { - n := p.handoff - if n == 0 { - print("runtime: phase error during cpu profile handoff\n") - return nil - } - if n&0x80000000 != 0 { - p.wtoggle = 1 - p.wtoggle - p.wholding = false - p.flushing = true - goto Flush - } - if cas(&p.handoff, n, 0) { - break - } - } - p.wtoggle = 1 - p.wtoggle - p.wholding = false - } - - if p.flushing { - goto Flush - } - - if !p.on && p.handoff == 0 { - return nil - } - - // Wait for new log. - notetsleepg(&p.wait, -1) - noteclear(&p.wait) - - switch n := p.handoff; { - case n == 0: - print("runtime: phase error during cpu profile wait\n") - return nil - case n == 0x80000000: - p.flushing = true - goto Flush - default: - n &^= 0x80000000 - - // Return new log to caller. - p.wholding = true - - return uintptrBytes(p.log[p.wtoggle][:n]) - } - - // In flush mode. - // Add is no longer being called. We own the log. - // Also, p->handoff is non-zero, so flushlog will return false. - // Evict the hash table into the log and return it. -Flush: - for i := range p.hash { - b := &p.hash[i] - for j := range b.entry { - e := &b.entry[j] - if e.count > 0 && !p.evict(e) { - // Filled the log. Stop the loop and return what we've got. - break Flush - } - } - } - - // Return pending log data. - if p.nlog > 0 { - // Note that we're using toggle now, not wtoggle, - // because we're working on the log directly. - n := p.nlog - p.nlog = 0 - return uintptrBytes(p.log[p.toggle][:n]) - } - - // Made it through the table without finding anything to log. - if !p.eodSent { - // We may not have space to append this to the partial log buf, - // so we always return a new slice for the end-of-data marker. - p.eodSent = true - return uintptrBytes(eod[:]) - } - - // Finally done. Clean up and return nil. - p.flushing = false - if !cas(&p.handoff, p.handoff, 0) { - print("runtime: profile flush racing with something\n") - } - return nil -} - -func uintptrBytes(p []uintptr) (ret []byte) { - pp := (*sliceStruct)(unsafe.Pointer(&p)) - rp := (*sliceStruct)(unsafe.Pointer(&ret)) - - rp.array = pp.array - rp.len = pp.len * int(unsafe.Sizeof(p[0])) - rp.cap = rp.len - - return -} - -// CPUProfile returns the next chunk of binary CPU profiling stack trace data, -// blocking until data is available. If profiling is turned off and all the profile -// data accumulated while it was on has been returned, CPUProfile returns nil. -// The caller must save the returned data before calling CPUProfile again. -// -// Most clients should use the runtime/pprof package or -// the testing package's -test.cpuprofile flag instead of calling -// CPUProfile directly. -func CPUProfile() []byte { - return cpuprof.getprofile() -} |