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Re: [HACKERS] spin locks

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: scrappy(at)hub(dot)org (The Hermit Hacker)
Cc: dz(at)cs(dot)unitn(dot)it, hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] spin locks
Date: 1998-03-16 05:08:03
Message-ID: 199803160508.AAA22455@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
> 
> On Sun, 15 Feb 1998, Bruce Momjian wrote:
> 
> > > 	I'm not quite sure I follow this...in a multi-cpu environment,
> > > would process_yield() introduce a problem? *raised eyebrow*
> > 
> > Probably.  I would leave the code as-is for multi-cpu systems.
> 
> 	So...how would we determine which is which? *raised eyebrow*
> 
> > Yep, but we need to check for multiple cpu's first before enabling it. 
> > That would be a good trick from configure.
> 
> 	I'm curious, still, as to whether this function would help
> performance on a multi-cpu environment as well...what if 2 processes are
> running on one of two CPUs, and another 2 on the other? *raised eyebrow*

Good point.  You would almost need to know if the one holding the lock
was currently running.  But it wouldn't be un-runnable while it was
holding the spinlock, so it should be run-able, even if it is not
currently running.

-- 
Bruce Momjian                          |  830 Blythe Avenue
maillist(at)candle(dot)pha(dot)pa(dot)us              |  Drexel Hill, Pennsylvania 19026
  +  If your life is a hard drive,     |  (610) 353-9879(w)
  +  Christ can be your backup.        |  (610) 853-3000(h)

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