code review 7413049: runtime: add garbage collector statistics

runtime: add garbage collector statistics

If the constant CollectStats is non-zero and GOGCTRACE=1
the garbage collector will print basic statistics about executed
GC instructions.

[atom, 2013-03-03 08:41:42]

Hello golang-dev@googlegroups.com (cc: rsc),

I'd like you to review this change to
https://go.googlecode.com/hg/

[dvyukov, 2013-03-03 08:56:20]

On Sun, Mar 3, 2013 at 10:41 AM,  <0xE2.0x9A.0x9B@gmail.com> wrote:
> Reviewers: golang-dev1,
>
> Message:
> Hello golang-dev@googlegroups.com (cc: rsc),
>
> I'd like you to review this change to
> https://go.googlecode.com/hg/
>
>
> Description:
> runtime: add garbage collector statistics
>
> If the constant CollectStats is non-zero and GOGCTRACE=1
> the garbage collector will print basic statistics about executed
> GC instructions.
>
> Please review this at https://codereview.appspot.com/7413049/
>
> Affected files:
>   M src/pkg/runtime/mgc0.c
>
>
> Index: src/pkg/runtime/mgc0.c
> ===================================================================
> --- a/src/pkg/runtime/mgc0.c
> +++ b/src/pkg/runtime/mgc0.c
> @@ -17,6 +17,7 @@
>  enum {
>         Debug = 0,
>         DebugMark = 0,  // run second pass to check mark
> +       CollectStats = 0,
>
>         // Four bits per word (see #defines below).
>         wordsPerBitmapWord = sizeof(void*)*8/4,
> @@ -165,8 +166,25 @@
>         GC_DEFAULT_PTR = GC_NUM_INSTR,
>         GC_MAP_NEXT,
>         GC_CHAN,
> +
> +       GC_NUM_INSTR2
>  };
>
> +static struct {
> +       uint64 ptr_sum;

The codebase does not use underscores FWIW

> +       uint64 ptr_cnt;
> +       uint64 nbytes;
> +       uint64 nobj_sum;
> +       uint64 nobj_cnt;
> +       uint64 nobj_notype;
> +       uint64 nobj_typelookups_ok;
> +       uint64 rescans;
> +       uint64 rescan_nbytes;
> +       uint64 instr[GC_NUM_INSTR2];
> +       uint64 putempty;
> +       uint64 getfull;
> +} gcstats;
> +
>  // markonly marks an object. It returns true if the object
>  // has been marked by this function, false otherwise.
>  // This function isn't thread-safe and doesn't append the object to any
> buffer.
> @@ -315,6 +333,11 @@
>         n = ptrbuf_end - ptrbuf;
>         *ptrbufpos = ptrbuf;
>
> +       if(CollectStats) {
> +               runtime·xadd64(&gcstats.ptr_sum, n);
> +               runtime·xadd64(&gcstats.ptr_cnt, 1);
> +       }
> +
>         // If buffer is nearly full, get a new one.
>         if(wbuf == nil || nobj+n >= nelem(wbuf->obj)) {
>                 if(wbuf != nil)
> @@ -621,6 +644,12 @@
>                         runtime·printf("scanblock %p %D\n", b, (int64)n);
>                 }
>
> +               if(CollectStats) {
> +                       runtime·xadd64(&gcstats.nbytes, n);
> +                       runtime·xadd64(&gcstats.nobj_sum, nobj);
> +                       runtime·xadd64(&gcstats.nobj_cnt, 1);
> +               }
> +
>                 if(ti != 0) {
>                         pc = (uintptr*)(ti & ~(uintptr)PC_BITS);
>                         precise_type = (ti & PRECISE);
> @@ -634,8 +663,14 @@
>                                 stack_top.count = 1;
>                         }
>                 } else if(UseSpanType) {
> +                       if(CollectStats)
> +                               runtime·xadd64(&gcstats.nobj_notype, 1);
> +
>                         type = runtime·gettype(b);
>                         if(type != 0) {
> +                               if(CollectStats)
> +
> runtime·xadd64(&gcstats.nobj_typelookups_ok, 1);
> +
>                                 t = (Type*)(type & ~(uintptr)(PtrSize-1));
>                                 switch(type & (PtrSize-1)) {
>                                 case TypeInfo_SingleObject:
> @@ -692,6 +727,9 @@
>                 end_b = (uintptr)b + n - PtrSize;
>
>         for(;;) {
> +               if(CollectStats)
> +                       runtime·xadd64(&gcstats.instr[pc[0]], 1);
> +
>                 obj = nil;
>                 objti = 0;
>                 switch(pc[0]) {
> @@ -1164,6 +1202,9 @@
>  static void
>  putempty(Workbuf *b)
>  {
> +       if(CollectStats)
> +               runtime·xadd64(&gcstats.putempty, 1);
> +
>         runtime·lfstackpush(&work.empty, &b->node);
>  }
>
> @@ -1173,6 +1214,9 @@
>  {
>         int32 i;
>
> +       if(CollectStats)
> +               runtime·xadd64(&gcstats.getfull, 1);
> +
>         if(b != nil)
>                 runtime·lfstackpush(&work.empty, &b->node);
>         b = (Workbuf*)runtime·lfstackpop(&work.full);
> @@ -1747,7 +1791,7 @@
>  gc(struct gc_args *args)
>  {
>         int64 t0, t1, t2, t3, t4;
> -       uint64 heap0, heap1, obj0, obj1;
> +       uint64 heap0, heap1, obj0, obj1, ninstr;
>         GCStats stats;
>         M *mp;
>         uint32 i;
> @@ -1764,6 +1808,9 @@
>         m->gcing = 1;
>         runtime·stoptheworld();
>
> +       if(CollectStats)
> +               runtime·memclr((byte*)&gcstats, sizeof(gcstats));
> +
>         for(mp=runtime·allm; mp; mp=mp->alllink)
>                 runtime·settype_flush(mp, false);
>
> @@ -1859,6 +1906,27 @@
>                         stats.nhandoff, stats.nhandoffcnt,
>                         work.sweepfor->nsteal, work.sweepfor->nstealcnt,
>                         stats.nprocyield, stats.nosyield, stats.nsleep);
> +               if(CollectStats) {
> +                       runtime·printf("scan: %D bytes, %D objects, %D
> untyped, %D types from MSpan\n",
> +                               gcstats.nbytes, gcstats.nobj_cnt,
> gcstats.nobj_notype, gcstats.nobj_typelookups_ok);
> +                       if(gcstats.ptr_cnt != 0)
> +                               runtime·printf("avg ptrbufsize: %D
> (%D/%D)\n",
> +                                       gcstats.ptr_sum/gcstats.ptr_cnt,
> gcstats.ptr_sum, gcstats.ptr_cnt);
> +                       if(gcstats.nobj_cnt != 0)
> +                               runtime·printf("avg nobj: %D (%D/%D)\n",
> +                                       gcstats.nobj_sum/gcstats.nobj_cnt,
> gcstats.nobj_sum, gcstats.nobj_cnt);
> +                       runtime·printf("rescans: %D, %D bytes\n",
> gcstats.rescans, gcstats.rescan_nbytes);
> +
> +                       runtime·printf("instruction counts:\n");
> +                       ninstr = 0;
> +                       for(i=0; i<nelem(gcstats.instr); i++) {
> +                               runtime·printf("\t%d:\t%D\n", i,
> gcstats.instr[i]);
> +                               ninstr += gcstats.instr[i];
> +                       }
> +                       runtime·printf("\ttotal:\t%D\n", ninstr);
> +
> +                       runtime·printf("putempty: %D, getfull: %D\n",
> gcstats.putempty, gcstats.getfull);
> +               }
>         }
>
>         runtime·MProf_GC();
>
>
> --
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[atom, 2013-03-03 09:01:29]

On 2013/03/03 08:56:20, dvyukov wrote:
> On Sun, Mar 3, 2013 at 10:41 AM,  <mailto:0xE2.0x9A.0x9B@gmail.com> wrote:
> >
> > +static struct {
> > +       uint64 ptr_sum;
> 
> The codebase does not use underscores FWIW
> 
> > +       uint64 ptr_cnt;
> > +       uint64 nbytes;
> > +       uint64 nobj_sum;
> > +       uint64 nobj_cnt;
> > +       uint64 nobj_notype;
> > +       uint64 nobj_typelookups_ok;

How to rename nobj_typelookups_ok?

> > +       uint64 rescans;
> > +       uint64 rescan_nbytes;
> > +       uint64 instr[GC_NUM_INSTR2];
> > +       uint64 putempty;
> > +       uint64 getfull;
> > +} gcstats;
> > +

[dvyukov, 2013-03-03 09:04:05]

On 2013/03/03 09:01:29, atom wrote:
> On 2013/03/03 08:56:20, dvyukov wrote:
> > On Sun, Mar 3, 2013 at 10:41 AM,  <mailto:0xE2.0x9A.0x9B@gmail.com> wrote:
> > >
> > > +static struct {
> > > +       uint64 ptr_sum;
> > 
> > The codebase does not use underscores FWIW
> > 
> > > +       uint64 ptr_cnt;
> > > +       uint64 nbytes;
> > > +       uint64 nobj_sum;
> > > +       uint64 nobj_cnt;
> > > +       uint64 nobj_notype;
> > > +       uint64 nobj_typelookups_ok;
> 
> How to rename nobj_typelookups_ok?

ntypelookup?

[atom, 2013-03-03 09:48:08]

Hello golang-dev@googlegroups.com, dvyukov@google.com (cc:
golang-dev@googlegroups.com, rsc@golang.org),

Please take another look.

[dvyukov, 2013-03-03 15:32:37]

LGTM

[rsc, 2013-03-04 15:22:50]

LGTM

[atom, 2013-03-04 15:54:45]

*** Submitted as https://code.google.com/p/go/source/detail?r=a565c143b41b ***

runtime: add garbage collector statistics

If the constant CollectStats is non-zero and GOGCTRACE=1
the garbage collector will print basic statistics about executed
GC instructions.

R=golang-dev, dvyukov
CC=golang-dev, rsc
https://codereview.appspot.com/7413049