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* rts: Use BITS_IN macro in bitmap calculationsÖmer Sinan Ağacan2018-02-061-2/+2
| | | | | | | | | | Reviewers: bgamari, erikd, simonmar Reviewed By: bgamari Subscribers: rwbarton, thomie, carter Differential Revision: https://phabricator.haskell.org/D4386
* Make RTS keep less memory (fixes #14702)Andrey Sverdlichenko2018-01-311-10/+42
| | | | | | | | | | | | | | | | | | | | | | | | Currently runtime keeps hold to 4*used_memory. This includes, in particular, nursery, which can be quite large on multiprocessor machines: 16 CPUs x 64Mb each is 1GB. Multiplying it by 4 means whatever actual memory usage is, runtime will never release memory under 4GB, and this is quite excessive for processes which only need a lot of memory shortly (think building data structures from large files). This diff makes multiplier to apply only to GC-managed memory, leaving all "static" allocations alone. Test Plan: make test TEST="T14702" Reviewers: bgamari, erikd, simonmar Reviewed By: simonmar Subscribers: rwbarton, thomie, carter GHC Trac Issues: #14702 Differential Revision: https://phabricator.haskell.org/D4338
* [rts] Adjust whitehole_spinDouglas Wilson2018-01-211-0/+4
| | | | | | | | | | | | | | | | | | | Rename to whitehole_gc_spin, in preparation for adding stats for the whitehole busy-loop in SMPClosureOps. Make whitehole_gc_spin volatile, and move it to be defined and statically initialised in GC.c. This saves some #ifs, and I'm pretty sure it should be volatile. Test Plan: ./validate Reviewers: bgamari, erikd, simonmar Reviewed By: bgamari Subscribers: rwbarton, thomie, carter Differential Revision: https://phabricator.haskell.org/D4300
* Detect overly long GC syncSimon Marlow2017-11-161-5/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: GC sync is the time between a GC being intiated and all the mutator threads finally stopping so that the GC can start. Problems that cause the GC sync to be delayed are hard to find and can cause dramatic slowdowns for heavily parallel programs. The new flag --long-gc-sync=<time> helps by emitting a warning and calling a user-overridable hook when the GC sync time exceeds the specified threshold. A debugger can be used to set a breakpoint when this happens and inspect the stacks of threads to find the culprit. Test Plan: ``` $ ./inplace/bin/ghc-stage2 +RTS --long-gc-sync=0.0000001 -S Alloc Copied Live GC GC TOT TOT Page Flts bytes bytes bytes user elap user elap 1135856 51144 153736 0.000 0.000 0.002 0.002 0 0 (Gen: 0) 1034760 94704 188752 0.000 0.000 0.002 0.002 0 0 (Gen: 0) 1038888 134832 228888 0.009 0.009 0.011 0.011 0 0 (Gen: 1) 1025288 90128 235184 0.000 0.000 0.012 0.012 0 0 (Gen: 0) 1049088 130080 333984 0.000 0.000 0.013 0.013 0 0 (Gen: 0) Warning: waited 0us for GC sync 1034424 73360 331976 0.000 0.000 0.013 0.013 0 0 (Gen: 0) ``` Also tested on a real production problem. Reviewers: niteria, bgamari, erikd Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D4193
* Fix Work Balance computation in RTS statsDouglas Wilson2017-07-111-3/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | An additional stat is tracked per gc: par_balanced_copied This is the the number of bytes copied by each gc thread under the balanced lmit, which is simply (copied_bytes / num_gc_threads). The stat is added to all the appropriate GC structures, so is visible in the eventlog and in GHC.Stats. A note is added explaining how work balance is computed. Remove some end of line whitespace Test Plan: ./validate experiment with the program attached to the ticket examine code changes carefully Reviewers: simonmar, austin, hvr, bgamari, erikd Reviewed By: simonmar Subscribers: Phyx, rwbarton, thomie GHC Trac Issues: #13830 Differential Revision: https://phabricator.haskell.org/D3658
* Prefer #if defined to #ifdefBen Gamari2017-04-281-14/+14
| | | | Our new CPP linter enforces this.
* Report heap overflow in the same way as stack overflowSimon Marlow2017-04-021-0/+11
| | | | | | | | | | | | | | | | | | | | | | | Now that we throw an exception for heap overflow, we should only print the heap overflow message in the main thread when the HeapOverflow exception is caught, rather than as a side effect in the GC. Stack overflows were already done this way, I just made heap overflow consistent with stack overflow, and did some related cleanup. Fixes broken T2592(profasm) which was reporting the heap overflow message twice (you would only notice when building with profiling libs enabled). Test Plan: validate Reviewers: bgamari, niteria, austin, DemiMarie, hvr, erikd Reviewed By: bgamari Subscribers: rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3394
* rts: Correct the nursery size in the gen 1 growth computationJohn C. Carey2017-02-231-1/+13
| | | | | | | | | | | | Fixes trac issue #13288. Reviewers: austin, bgamari, erikd, simonmar Reviewed By: simonmar Subscribers: mutjida, rwbarton, thomie Differential Revision: https://phabricator.haskell.org/D3143
* Overhaul GC statsSimon Marlow2016-12-061-5/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: Visible API changes: * The C struct `GCDetails` gives the stats about a single GC. This is passed to the `gcDone()` callback if one is set via the RtsConfig. (previously we just passed a collection of values, so this is more extensible, at the expense of breaking the existing API) * `RTSStats` gives cumulative stats since the start of the program, and includes the `GCDetails` for the most recent GC. This struct can be obtained via `getRTSStats()` (the old `getGCStats()` has been removed, and `getGCStatsEnabled()` has been renamed to `getRTSStatsEnabled()`) Improvements: * The per-GC stats and cumulative stats are now cleanly separated. * Inside the RTS we have a top-level `RTSStats` struct to keep all our stats in, previously this was just a collection of strangely-named variables. This struct is mostly just copied in `getRTSStats()`, so the implementation of that function is a lot shorter. * Types are more consistent. We use a uint64_t byte count for all memory values, and Time for all time values. * Names are more consistent. We use a suffix `_bytes` for all byte counts and `_ns` for all time values. * We now collect information about the amount of memory in large objects and compact objects in `GCDetails`. (the latter was the reason I started doing this patch but it seems to have ballooned a bit!) * I fixed a bug in the calculation of the elapsed MUT time, and added an ASSERT to stop the calculations going wrong in the future. For now I kept the Haskell API in `GHC.Stats` the same, by impedence-matching with the new API. We could either break that API and make it match the C API more closely, or we could add a new API and deprecate the old one. Opinions welcome. This stuff is very easy to get wrong, and it's hard to test. Reviews welcome! Test Plan: manual testing validate Reviewers: bgamari, niteria, austin, ezyang, hvr, erikd, rwbarton, Phyx Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2756
* Use C99's boolBen Gamari2016-11-291-30/+30
| | | | | | | | | | | | Test Plan: Validate on lots of platforms Reviewers: erikd, simonmar, austin Reviewed By: erikd, simonmar Subscribers: michalt, thomie Differential Revision: https://phabricator.haskell.org/D2699
* Fix a bug in parallel GC synchronisationSimon Marlow2016-10-291-18/+21
| | | | | | | | | | | | | | | | | | | | | Summary: The problem boils down to global variables: in particular gc_threads[], which was being modified by a subsequent GC before the previous GC had finished with it. The fix is to not use global variables. This was causing setnumcapabilities001 to fail (again!). It's an old bug though. Test Plan: Ran setnumcapabilities001 in a loop for a couple of hours. Before this patch it had been failing after a few minutes. Not a very scientific test, but it's the best I have. Reviewers: bgamari, austin, fryguybob, niteria, erikd Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2654
* Move stat_startGCSyncBartosz Nitka2016-07-271-2/+0
| | | | | | | | | | | | | | @simonmar told me that it makes more sense this way. Test Plan: it still builds Reviewers: bgamari, austin, simonmar, erikd Reviewed By: simonmar, erikd Subscribers: thomie, simonmar Differential Revision: https://phabricator.haskell.org/D2428
* Compact RegionsGiovanni Campagna2016-07-201-1/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | This brings in initial support for compact regions, as described in the ICFP 2015 paper "Efficient Communication and Collection with Compact Normal Forms" (Edward Z. Yang et.al.) and implemented by Giovanni Campagna. Some things may change before the 8.2 release, but I (Simon M.) wanted to get the main patch committed so that we can iterate. What documentation there is is in the Data.Compact module in the new compact package. We'll need to extend and polish the documentation before the release. Test Plan: validate (new test cases included) Reviewers: ezyang, simonmar, hvr, bgamari, austin Subscribers: vikraman, Yuras, RyanGlScott, qnikst, mboes, facundominguez, rrnewton, thomie, erikd Differential Revision: https://phabricator.haskell.org/D1264 GHC Trac Issues: #11493
* Rts flags cleanupSimon Marlow2016-06-101-4/+4
| | | | | | | | * Remove unused/old flags from the structs * Update old comments * Add missing flags to GHC.RTS * Simplify GHC.RTS, remove C code and use hsc2hs instead * Make ParFlags unconditional, and add support to GHC.RTS
* NUMA supportSimon Marlow2016-06-101-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: The aim here is to reduce the number of remote memory accesses on systems with a NUMA memory architecture, typically multi-socket servers. Linux provides a NUMA API for doing two things: * Allocating memory local to a particular node * Binding a thread to a particular node When given the +RTS --numa flag, the runtime will * Determine the number of NUMA nodes (N) by querying the OS * Assign capabilities to nodes, so cap C is on node C%N * Bind worker threads on a capability to the correct node * Keep a separate free lists in the block layer for each node * Allocate the nursery for a capability from node-local memory * Allocate blocks in the GC from node-local memory For example, using nofib/parallel/queens on a 24-core 2-socket machine: ``` $ ./Main 15 +RTS -N24 -s -A64m Total time 173.960s ( 7.467s elapsed) $ ./Main 15 +RTS -N24 -s -A64m --numa Total time 150.836s ( 6.423s elapsed) ``` The biggest win here is expected to be allocating from node-local memory, so that means programs using a large -A value (as here). According to perf, on this program the number of remote memory accesses were reduced by more than 50% by using `--numa`. Test Plan: * validate * There's a new flag --debug-numa=<n> that pretends to do NUMA without actually making the OS calls, which is useful for testing the code on non-NUMA systems. * TODO: I need to add some unit tests Reviewers: erikd, austin, rwbarton, ezyang, bgamari, hvr, niteria Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2199
* rts: Replace `nat` with `uint32_t`Erik de Castro Lopo2016-05-051-37/+37
| | | | | | | | | | | | The `nat` type was an alias for `unsigned int` with a comment saying it was at least 32 bits. We keep the typedef in case client code is using it but mark it as deprecated. Test Plan: Validated on Linux, OS X and Windows Reviewers: simonmar, austin, thomie, hvr, bgamari, hsyl20 Differential Revision: https://phabricator.haskell.org/D2166
* Allow limiting the number of GC threads (+RTS -qn<n>)Simon Marlow2016-05-041-3/+1
| | | | | | | | | | | | | | | | | | This allows the GC to use fewer threads than the number of capabilities. At each GC, we choose some of the capabilities to be "idle", which means that the thread running on that capability (if any) will sleep for the duration of the GC, and the other threads will do its work. We choose capabilities that are already idle (if any) to be the idle capabilities. The idea is that this helps in the following situation: * We want to use a large -N value so as to make use of hyperthreaded cores * We use a large heap size, so GC is infrequent * But we don't want to use all -N threads in the GC, because that thrashes the memory too much. See docs for usage.
* Allocate blocks in the GC in batchesSimon Marlow2016-04-121-1/+1
| | | | | | | | | | | | | | | | | Avoids contention for the block allocator lock in the GC; this can be seen in the gc_alloc_block_sync counter emitted by +RTS -s. I experimented with this a while ago, and there was already commented-out code for it in GCUtils.c, but I've now improved it so that it doesn't result in significantly worse memory usage. * The old method of putting spare blocks on ws->part_list was wasteful, the spare blocks are now shared between all generations and retained between GCs. * repeated allocGroup() results in fragmentation, so I switched to using allocLargeChunk() instead which is fragmentation-friendly; we already use it for the same reason in nursery allocation.
* Cache the size of part_list/scavd_list (#11783)Simon Marlow2016-04-121-1/+6
| | | | | | | | | After a parallel GC, it is possible to have a long list of blocks in ws->part_list, if we did a lot of work stealing but didn't fill up the blocks we stole. These blocks persist until the next load-balanced GC, which might be a long time, and during every GC we were traversing this list to find its size. The fix is to maintain the size all the time, so we don't have to compute it.
* rts: mark 'copied' as staticSergei Trofimovich2016-02-071-1/+1
| | | | | | | | Noticed by uselex.rb: copied: [R]: exported from: ./rts/dist/build/sm/GC.o Signed-off-by: Sergei Trofimovich <siarheit@google.com>
* rts: Kill PAPI supportBen Gamari2015-11-181-18/+0
| | | | | | | | | | | | | | | This hasn't been used for a very long time and will soon be superceded by perf_events support. Test Plan: validate Reviewers: austin, simonmar Reviewed By: austin, simonmar Subscribers: thomie, erikd Differential Revision: https://phabricator.haskell.org/D1493
* Eliminate zero_static_objects_list()Simon Marlow2015-07-281-36/+12
| | | | | | | | | | | | | | | | | | | | | | | | | Summary: [Revised version of D1076 that was committed and then backed out] In a workload with a large amount of code, zero_static_objects_list() takes a significant amount of time, and furthermore it is in the single-threaded part of the GC. This patch uses a slightly fiddly scheme for marking objects on the static object lists, using a flag in the low 2 bits that flips between two states to indicate whether an object has been visited during this GC or not. We also have to take into account objects that have not been visited yet, which might appear at any time due to runtime linking. Test Plan: validate Reviewers: austin, ezyang, rwbarton, bgamari, thomie Reviewed By: bgamari, thomie Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1106
* Revert "Eliminate zero_static_objects_list()"Simon Marlow2015-07-271-12/+36
| | | | This reverts commit b949c96b4960168a3b399fe14485b24a2167b982.
* Eliminate zero_static_objects_list()Simon Marlow2015-07-221-36/+12
| | | | | | | | | | | | | | | | | | | | | Summary: In a workload with a large amount of code, zero_static_objects_list() takes a significant amount of time, and furthermore it is in the single-threaded part of the GC. This patch uses a slightly fiddly scheme for marking objects on the static object lists, using a flag in the low 2 bits that flips between two states to indicate whether an object has been visited during this GC or not. We also have to take into account objects that have not been visited yet, which might appear at any time due to runtime linking. Test Plan: validate Reviewers: austin, bgamari, ezyang, rwbarton Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D1076
* Replace hooks by callbacks in RtsConfig (#8785)Simon Marlow2015-04-071-0/+3
| | | | | | | | | | | | Summary: Hooks rely on static linking semantics, and are broken by -Bsymbolic which we need when using dynamic linking. Test Plan: Built it Reviewers: austin, hvr, tibbe Differential Revision: https://phabricator.haskell.org/D8
* Add +RTS -n<size>: divide the nursery into chunksSimon Marlow2014-11-251-26/+3
| | | | See the documentation for details.
* [skip ci] rts: Detabify sm/GC.cAustin Seipp2014-10-211-164/+164
| | | | Signed-off-by: Austin Seipp <austin@well-typed.com>
* Name worker threads using pthread_setname_npSimon Marlow2014-10-101-8/+9
| | | | | This helps identify threads in gdb particularly in processes with a lot of threads.
* Revert "rts: add Emacs 'Local Variables' to every .c file"Simon Marlow2014-09-291-8/+0
| | | | This reverts commit 39b5c1cbd8950755de400933cecca7b8deb4ffcd.
* rts: add Emacs 'Local Variables' to every .c fileAustin Seipp2014-07-281-0/+8
| | | | | | | | This will hopefully help ensure some basic consistency in the forward by overriding buffer variables. In particular, it sets the wrap length, the offset to 4, and turns off tabs. Signed-off-by: Austin Seipp <austin@well-typed.com>
* Avoid unnecessary clock_gettime() syscalls in GC stats.Brian Brooks2014-07-101-5/+0
| | | | | | | | | | | | | | Summary: Avoid unnecessary clock_gettime() syscalls in GC stats. Test Plan: Use strace. Reviewers: simonmar, austin Reviewed By: simonmar, austin Subscribers: simonmar, relrod, carter Differential Revision: https://phabricator.haskell.org/D39
* Per-capability nursery weak pointer lists, fixes #9075Edward Z. Yang2014-05-291-0/+3
| | | | Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>
* rts: Fix possible int overflow in resize_nurseryAustin Seipp2014-04-271-1/+2
| | | | | | | | | | | n_capabilities is declared as unsigned int (32bit), and so multiplication is 32-bit before being stored in a 64bit integer (StgWord). Instead, cast n_capabilities to StgWord before multiplying. Discovered by Coverity. CID 43164. Signed-off-by: Austin Seipp <austin@well-typed.com>
* Fix windows x86_64 build.Austin Seipp2013-12-091-1/+1
| | | | | | | On win64 sizeof(long) != sizeof(void*), so debugTrace was casting a value of incorrect size causing a validate failure. Signed-off-by: Austin Seipp <austin@well-typed.com>
* Call busy_wait_nop() in the spin-wait loop in shutdown_gc_threads()Patrick Palka2013-11-291-1/+4
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* Allow the linker to be used without retaining CAFs unconditionallySimon Marlow2013-11-211-4/+4
| | | | | | | | | This creates a new C API: initLinker_ (int retain_cafs) The old initLinker() was left as-is for backwards compatibility. See documentation in Linker.h.
* In the DEBUG rts, track when CAFs are GC'dSimon Marlow2013-11-211-29/+27
| | | | | | | | | | | | This resurrects some old code and makes it work again. The idea is that we want to get an error message if we ever enter a CAF that has been GC'd, rather than following its indirection which will likely cause a segfault. Without this patch, these bugs are hard to track down in gdb, because the IND_STATIC code overwrites R1 (the pointer to the CAF) with its indirectee before jumping into bad memory, so we've lost the address of the CAF that got GC'd. Some associated refactoring while I was here.
* Initialize gc_thread.mut_spin to the 'acquired' statePatrick Palka2013-10-021-0/+1
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* Globally replace "hackage.haskell.org" with "ghc.haskell.org"Simon Marlow2013-10-011-1/+1
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* Don't move Capabilities in setNumCapabilities (#8209)Simon Marlow2013-09-041-28/+22
| | | | | | | | | | | | | We have various problems with reallocating the array of Capabilities, due to threads in waitForReturnCapability that are already holding a pointer to a Capability. Rather than add more locking to make this safer, I decided it would be easier to ensure that we never move the Capabilities at all. The capabilities array is now an array of pointers to Capabaility. There are extra indirections, but it rarely matters - we don't often access Capabilities via the array, normally we already have a pointer to one. I ran the parallel benchmarks and didn't see any difference.
* Merge branch 'master' into atomicsRyan Newton2013-08-311-0/+5
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| * Really unload object code when it is safe to do so (#8039)Simon Marlow2013-08-221-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The next major GC after an unloadObj() will do a traversal of the heap to determine whether the object code can be removed from memory or not. We'll keep doing these until it is safe to remove the object code. In my experiments with GHCi, the objects get unloaded immediately, which is a good sign: we're not accidentally holding on to any references anywhere in the GHC data structures. Changes relative to the patch earlier posted on the ticket: - fix two memory leaks discovered with Valgrind, after testing with tests/rts/linker_unload.c
* | Eliminate atomic_inc_by and instead medofiy atomic_inc.Ryan Newton2013-08-211-1/+1
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* Maintain per-generation lists of weak pointers (#7847)Takano Akio2013-06-151-1/+1
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* Kill dead code.Austin Seipp2013-05-121-101/+86
| | | | Signed-off-by: Austin Seipp <aseipp@pobox.com>
* Separate StablePtr and StableName tables (#7674)Simon Marlow2013-02-141-6/+6
| | | | To improve performance of StablePtr.
* Simplify the allocation stats accountingSimon Marlow2013-02-141-23/+10
| | | | | | | | | | | We were doing it in two different ways and asserting that the results were the same. In most cases they were, but I found one case where they weren't: the GC itself allocates some memory for running finalizers, and this memory was accounted for one way but not the other. It was simpler to remove the old way of counting allocation that to try to fix it up, so I did that.
* Rearrange includes to avoid a clash on ARM/LinuxSimon Marlow2013-01-171-12/+13
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* Add a write barrier for TVAR closuresSimon Marlow2012-11-161-2/+20
| | | | | | | | | | This improves GC performance when there are a lot of TVars in the heap. For instance, a TChan with a lot of elements causes a massive GC drag without this patch. There's more to do - several other STM closure types don't have write barriers, so GC performance when there are a lot of threads blocked on STM isn't great. But fixing the problem for TVar is a good start.
* Don't clearNurseries() in parallel with -debugSimon Marlow2012-11-011-3/+5
| | | | It makes sanity-checking fail.
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