On Sun, Jun 11, 2006 at 09:58:33PM -0400, Tom Lane wrote:
> Kris Kennaway <kris@obsecurity.org> writes:
> > On Sun, Jun 11, 2006 at 07:43:03PM -0400, Tom Lane wrote:
> >> Let's see the evidence.
>
> > The calls to setproctitle() (it looks like 4 setproctitle syscalls per
> > DB query) are causing contention on the Giant lock 25% of the time on
> > a dual p4 + HTT. Disabling process title setting completely gives an
> > 8% peak performance boost to the super-smack select benchmark.
>
> I think you misunderstood me: I asked for evidence, not interpretation.
> What are you measuring, and with what tool, and what are the numbers?
> On what benchmark case?
As I said, I'm using the super-smack select benchmark; presumably you
are aware of it.
> And what did you do to "disable process title setting completely"?
Added this to ps_status.c:
#undef PS_USE_SETPROCTITLE
#undef PS_USE_PSTAT
#undef PS_USE_PS_STRINGS
#undef PS_USE_CHANGE_ARGV
#undef PS_USE_CLOBBER_ARGV
#define PS_USE_NONE
Here are the queries/second data, before and after:
x pg
+ pg-noproctitle
+------------------------------------------------------------+
|x xx + |
|x xx + + |
|xx xxx + + + ++++ |
| |AM| |____AM___||
+------------------------------------------------------------+ N Min Max Median
Avg Stddev
x 11 3399.29 3425.1 3413.93 3411.8418 9.4287675
+ 10 3615.63 3699.32 3685.515 3679.344 24.894177
Difference at 95.0% confidence 267.502 +/- 16.871 7.8404% +/- 0.494483% (Student's t, pooled s =
18.4484)
Kris
