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Re: Wierd context-switching issue on Xeon

From: Dave Cramer <pg(at)fastcrypt(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: Anjan Dave <adave(at)vantage(dot)com>,Dirk Lutzeb├Ąck <lutzeb(at)aeccom(dot)com>,Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgreSQL(dot)org,Neil Conway <neilc(at)samurai(dot)com>
Subject: Re: Wierd context-switching issue on Xeon
Date: 2004-04-21 02:41:03
Message-ID: 1082515263.1558.214.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-performance
I modified the code in s_lock.c to remove the spins

#define SPINS_PER_DELAY         1

and it doesn't exhibit the behaviour

This effectively changes the code to 


while(TAS(lock))
	select(10000); // 10ms

Can anyone explain why executing TAS 100 times would increase context
switches ?

Dave


On Tue, 2004-04-20 at 12:59, Josh Berkus wrote:
> Anjan,
> 
> > Quad 2.0GHz XEON with highest load we have seen on the applications, DB
> > performing great -
> 
> Can you run Tom's test?   It takes a particular pattern of data access to 
> reproduce the issue.
-- 
Dave Cramer
519 939 0336
ICQ # 14675561


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