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Re: 7.3.8 under FC3 takes excessive semaphores?

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Mark Cave-Ayland <m(dot)cave-ayland(at)webbased(dot)co(dot)uk>
Cc: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: 7.3.8 under FC3 takes excessive semaphores?
Date: 2005-02-02 17:14:00
Message-ID: 200502021714.j12HE0I23254@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Mark Cave-Ayland wrote:
> 
> > -----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.

And with 7.4 and later we will throw a configure error if we don't find
native spinlocks so you will have no surprises in the future.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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