| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Wierd context-switching issue on Xeon |
| Date: | 2003-11-25 23:37:42 |
| Message-ID: | 200311251537.42527.josh@agliodbs.com |
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| Thread: | |
| Lists: | pgsql-performance |
Tom,
> Strictly a WAG ... but what this sounds like to me is disastrously bad
> behavior of the spinlock code under heavy contention. We thought we'd
> fixed the spinlock code for SMP machines awhile ago, but maybe
> hyperthreading opens some new vistas for misbehavior ...
Yeah, I thought of that based on the discussion on -Hackers. But we tried
turning off hyperthreading, with no change in behavior.
> If you can't try 7.4, or want to gather more data first, it would be
> good to try to confirm or disprove the theory that the context switches
> are coming from spinlock delays. If they are, they'd be coming from the
> select() calls in s_lock() in s_lock.c. Can you strace or something to
> see what kernel calls the context switches occur on?
Might be worth it ... will suggest that. Will also try 7.4.
--
-Josh Berkus
Aglio Database Solutions
San Francisco
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