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runtime: faster parallel GC

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Use per-thread work buffers instead of global mutex-protected pool. This eliminates contention from parallel scan phase.

benchmark                             old ns/op    new ns/op    delta
garbage.BenchmarkTree2-8               97100768     71417553  -26.45%
garbage.BenchmarkTree2LastPause-8     970931485    714103692  -26.45%
garbage.BenchmarkTree2Pause-8         469127802    345029253  -26.45%
garbage.BenchmarkParser-8            2880950854   2715456901   -5.74%
garbage.BenchmarkParserLastPause-8    137047399    103336476  -24.60%
garbage.BenchmarkParserPause-8         80686028     58922680  -26.97%

R=golang-dev, 0xe2.0x9a.0x9b, dave, adg, rsc, iant
CC=golang-dev
https://golang.org/cl/7816044
This commit is contained in:
Dmitriy Vyukov 2013-03-21 12:48:02 +04:00
parent 656bc3eb96
commit d4c80d19a8
2 changed files with 25 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
src/pkg/runtime/mgc0.c
View File

@ -140,6 +140,7 @@ static Workbuf* getempty(Workbuf*);
static Workbuf* getfull(Workbuf*);
static void putempty(Workbuf*);
static Workbuf* handoff(Workbuf*);
static void gchelperstart(void);
static struct {
uint64 full; // lock-free list of full blocks
@ -287,11 +288,12 @@ struct BufferList
{
PtrTarget ptrtarget[IntermediateBufferCapacity];
Obj obj[IntermediateBufferCapacity];
BufferList *next;
uint32 busy;
byte pad[CacheLineSize];
};
static BufferList *bufferList;
#pragma dataflag 16 // no pointers
static BufferList bufferList[MaxGcproc];
static Lock lock;
static Type *itabtype;
static void enqueue(Obj obj, Workbuf **_wbuf, Obj **_wp, uintptr *_nobj);
@ -598,23 +600,11 @@ scanblock(Workbuf *wbuf, Obj *wp, uintptr nobj, bool keepworking)
// Allocate ptrbuf
{
runtime·lock(&lock);
if(bufferList == nil) {
bufferList = runtime·SysAlloc(sizeof(*bufferList));
if(bufferList == nil)
runtime·throw("runtime: cannot allocate memory");
bufferList->next = nil;
}
scanbuffers = bufferList;
bufferList = bufferList->next;
scanbuffers = &bufferList[m->helpgc];
ptrbuf = &scanbuffers->ptrtarget[0];
ptrbuf_end = &scanbuffers->ptrtarget[0] + nelem(scanbuffers->ptrtarget);
objbuf = &scanbuffers->obj[0];
objbuf_end = &scanbuffers->obj[0] + nelem(scanbuffers->obj);
runtime·unlock(&lock);
}
ptrbufpos = ptrbuf;
@ -1056,11 +1046,7 @@ scanblock(Workbuf *wbuf, Obj *wp, uintptr nobj, bool keepworking)
nobj--;
}
endscan:
runtime·lock(&lock);
scanbuffers->next = bufferList;
bufferList = scanbuffers;
runtime·unlock(&lock);
endscan:;
}
// debug_scanblock is the debug copy of scanblock.
@ -1688,6 +1674,8 @@ runtime·memorydump(void)
void
runtime·gchelper(void)
{
gchelperstart();
// parallel mark for over gc roots
runtime·parfordo(work.markfor);
@ -1701,6 +1689,7 @@ runtime·gchelper(void)
}
runtime·parfordo(work.sweepfor);
bufferList[m->helpgc].busy = 0;
if(runtime·xadd(&work.ndone, +1) == work.nproc-1)
runtime·notewakeup(&work.alldone);
}
@ -1892,6 +1881,7 @@ gc(struct gc_args *args)
t1 = runtime·nanotime();
gchelperstart();
runtime·parfordo(work.markfor);
scanblock(nil, nil, 0, true);
@ -1903,6 +1893,7 @@ gc(struct gc_args *args)
t2 = runtime·nanotime();
runtime·parfordo(work.sweepfor);
bufferList[m->helpgc].busy = 0;
t3 = runtime·nanotime();
if(work.nproc > 1)
@ -2043,6 +2034,15 @@ runtime∕debug·setGCPercent(intgo in, intgo out)
FLUSH(&out);
}
static void
gchelperstart(void)
{
if(m->helpgc < 0 || m->helpgc >= MaxGcproc)
runtime·throw("gchelperstart: bad m->helpgc");
if(runtime·xchg(&bufferList[m->helpgc].busy, 1))
runtime·throw("gchelperstart: already busy");
}
static void
runfinq(void)
{

8
src/pkg/runtime/proc.c
View File

@ -332,7 +332,7 @@ runtime·helpgc(int32 nproc)
mp = mget();
if(mp == nil)
runtime·throw("runtime·gcprocs inconsistency");
mp->helpgc = 1;
mp->helpgc = n;
mp->mcache = runtime·allp[pos]->mcache;
pos++;
runtime·notewakeup(&mp->park);
@ -386,7 +386,7 @@ runtime·stoptheworld(void)
static void
mhelpgc(void)
{
m->helpgc = 1;
m->helpgc = -1;
}
void
@ -485,7 +485,7 @@ runtime·mstart(void)
m->mstartfn();
if(m->helpgc) {
m->helpgc = false;
m->helpgc = 0;
stopm();
} else if(m != &runtime·m0) {
acquirep(m->nextp);
@ -794,8 +794,8 @@ retry:
runtime·notesleep(&m->park);
runtime·noteclear(&m->park);
if(m->helpgc) {
m->helpgc = 0;
runtime·gchelper();
m->helpgc = 0;
m->mcache = nil;
goto retry;
}