| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Brent Verner <brent(at)rcfile(dot)org> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Some interesting results from tweaking spinlocks |
| Date: | 2002-01-05 22:04:36 |
| Message-ID: | 13361.1010268276@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Brent Verner <brent(at)rcfile(dot)org> writes:
> Using a single-processor machine, we're not going to get any lower
> sleep times than ~10ms from either usleep or select on linux, and
> usleep is always longer.
Ah, so usleep is just being stricter about rounding up the requested
delay? That would explain the results all right.
> Looks like increasing spins allows
> the process to get the lock before the usleep/select is run
Right. Up to a point, increasing spins improves the odds of acquiring
the lock without having to release the processor.
What I should've thought of is to try sched_yield() as well, which is
the operation we *really* want here, and it is available on this version
of Linux. Off to run another batch of tests ...
regards, tom lane
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