diff options
| author | Russ Cox <rsc@golang.org> | 2011-10-06 11:30:48 -0400 |
|---|---|---|
| committer | Russ Cox <rsc@golang.org> | 2011-10-06 11:30:48 -0400 |
| commit | ad35cea7622a6fb839f06bb5b46cee9110fa94a0 (patch) | |
| tree | 0472a0afaf739f32faa843d93f90a62f6e843ed3 /src/pkg/runtime | |
| parent | 56959158331072ed17801aa539a0d6f28064b511 (diff) | |
| download | go-ad35cea7622a6fb839f06bb5b46cee9110fa94a0.tar.xz | |
runtime: fix malloc sampling bug
The malloc sample trigger was not being set in a
new m, so the first allocation in each new m - the
goroutine structure - was being sampled with
probability 1 instead of probability sizeof(G)/rate,
an oversampling of about 5000x for the default
rate of 1 MB. This bug made pprof graphs show
far more G allocations than there actually were.
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5224041
Diffstat (limited to 'src/pkg/runtime')
| -rw-r--r-- | src/pkg/runtime/malloc.goc | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc index 84e0ac4795..6d2f65b3c9 100644 --- a/src/pkg/runtime/malloc.goc +++ b/src/pkg/runtime/malloc.goc @@ -80,6 +80,7 @@ runtime·mallocgc(uintptr size, uint32 flag, int32 dogc, int32 zeroed) m->mcache->next_sample -= size; else { // pick next profile time + // If you change this, also change allocmcache. if(rate > 0x3fffffff) // make 2*rate not overflow rate = 0x3fffffff; m->mcache->next_sample = runtime·fastrand1() % (2*rate); @@ -205,6 +206,7 @@ runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **sp) MCache* runtime·allocmcache(void) { + int32 rate; MCache *c; runtime·lock(&runtime·mheap); @@ -212,6 +214,13 @@ runtime·allocmcache(void) mstats.mcache_inuse = runtime·mheap.cachealloc.inuse; mstats.mcache_sys = runtime·mheap.cachealloc.sys; runtime·unlock(&runtime·mheap); + + // Set first allocation sample size. + rate = runtime·MemProfileRate; + if(rate > 0x3fffffff) // make 2*rate not overflow + rate = 0x3fffffff; + c->next_sample = runtime·fastrand1() % (2*rate); + return c; } |