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Re: 7.3.8 under FC3 takes excessive semaphores?

From: "Mark Cave-Ayland" <m(dot)cave-ayland(at)webbased(dot)co(dot)uk>
To: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 7.3.8 under FC3 takes excessive semaphores?
Date: 2005-02-01 12:40:09
Message-ID: 9EB50F1A91413F4FA63019487FCD251DADE6@WEBBASEDDC.webbasedltd.local (view raw or flat)
Thread:
Lists: pgsql-hackers
> -----Original Message-----
> From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] 
> Sent: 31 January 2005 16:35
> To: Mark Cave-Ayland
> Cc: pgsql-hackers(at)postgresql(dot)org
> Subject: Re: [HACKERS] 7.3.8 under FC3 takes excessive semaphores?

(cut)

> Judging by the symptoms, you have built a version with what 
> we now call --disable-spinlocks; that is, it didn't figure 
> out how to do assembly TAS on your platform and fell back to 
> using SysV semaphores for spinlocks. Quite aside from the 
> drain on semaphores, the performance is going to be 
> spectacularly bad, so you'd better fix that.
> 
> 			regards, tom lane


Hi Tom,

I'd just about managed to come to the same conclusion before your email
arrived by spending the afternoon with gdb tracing into the LWLock code :)

I've just installed 7.4.6 on the same box and this time the spinlocks are
correctly picked up and everything works as expected. I think rather than
fixing the 7.3.x source, we'll take the plunge and plan for a complete dump
and restore of the database cluster over a weekend.


Many thanks,

Mark.

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