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runtime: more precise mprof sampling

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Better sampling of objects that are close in size to sampling rate.
See the comment for details.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/43830043
This commit is contained in:
Dmitriy Vyukov 2014-02-12 22:36:45 +04:00
parent 5e72fae9b2
commit bf0d71af29
2 changed files with 35 additions and 13 deletions
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1
misc/pprof
View File

@ -2652,6 +2652,7 @@ sub RemoveUninterestingFrames {
'makechan',
'makemap',
'mal',
'profilealloc',
'runtime.new',
'makeslice1',
'runtime.malloc',

47
src/pkg/runtime/malloc.goc
View File

@ -28,6 +28,7 @@ extern MStats mstats; // defined in zruntime_def_$GOOS_$GOARCH.go
extern volatile intgo runtime·MemProfileRate;
static void* largealloc(uint32, uintptr*);
static void profilealloc(void *v, uintptr size, uintptr typ);
// Allocate an object of at least size bytes.
// Small objects are allocated from the per-thread cache's free lists.
@ -191,29 +192,23 @@ runtime·mallocgc(uintptr size, uintptr typ, uint32 flag)
runtime·settype_flush(m);
if(raceenabled)
runtime·racemalloc(v, size);
m->locks--;
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
g->stackguard0 = StackPreempt;
if(runtime·debug.allocfreetrace)
goto profile;
if(!(flag & FlagNoProfiling) && (rate = runtime·MemProfileRate) > 0) {
if(size >= rate)
goto profile;
if(m->mcache->next_sample > size)
m->mcache->next_sample -= size;
if(size < rate && size < c->next_sample)
c->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);
profile:
runtime·MProf_Malloc(v, size, typ);
profilealloc(v, size, typ);
}
}
m->locks--;
if(m->locks == 0 && g->preempt) // restore the preemption request in case we've cleared it in newstack
g->stackguard0 = StackPreempt;
if(!(flag & FlagNoInvokeGC) && mstats.heap_alloc >= mstats.next_gc)
runtime·gc(0);
@ -245,6 +240,32 @@ largealloc(uint32 flag, uintptr *sizep)
return v;
}
static void
profilealloc(void *v, uintptr size, uintptr typ)
{
uintptr rate;
int32 next;
MCache *c;
c = m->mcache;
rate = runtime·MemProfileRate;
if(size < rate) {
// pick next profile time
// If you change this, also change allocmcache.
if(rate > 0x3fffffff) // make 2*rate not overflow
rate = 0x3fffffff;
next = runtime·fastrand1() % (2*rate);
// Subtract the "remainder" of the current allocation.
// Otherwise objects that are close in size to sampling rate
// will be under-sampled, because we consistently discard this remainder.
next -= (size - c->next_sample);
if(next < 0)
next = 0;
c->next_sample = next;
}
runtime·MProf_Malloc(v, size, typ);
}
void*
runtime·malloc(uintptr size)
{