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| author | Simon Marlow <marlowsd@gmail.com> | 2015-02-11 14:19:21 +0000 |
|---|---|---|
| committer | Simon Marlow <marlowsd@gmail.com> | 2017-11-16 13:49:05 +0000 |
| commit | 2f4638735ad1526d6502a4706bffafffb93e24da (patch) | |
| tree | 8711e34b498ea52d0a8092fb763892c07c602d92 /rts/sm/GCThread.h | |
| parent | 07ac921f48baea84b40835b0b7c476806f7f63f6 (diff) | |
| download | haskell-2f4638735ad1526d6502a4706bffafffb93e24da.tar.gz | |
Detect overly long GC sync
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
Diffstat (limited to 'rts/sm/GCThread.h')
| -rw-r--r-- | rts/sm/GCThread.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/rts/sm/GCThread.h b/rts/sm/GCThread.h index bb206db64c..e865dabe5d 100644 --- a/rts/sm/GCThread.h +++ b/rts/sm/GCThread.h @@ -116,6 +116,12 @@ typedef struct gen_workspace_ { of the GC threads ------------------------------------------------------------------------- */ +/* values for the wakeup field */ +#define GC_THREAD_INACTIVE 0 +#define GC_THREAD_STANDING_BY 1 +#define GC_THREAD_RUNNING 2 +#define GC_THREAD_WAITING_TO_CONTINUE 3 + typedef struct gc_thread_ { Capability *cap; |