Horton

Re: Wierd context-switching issue on Xeon

Dave Cramer <pg@fastcrypt.com>

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From: Dave Cramer <pg@fastcrypt.com>
To: Josh Berkus <josh@agliodbs.com>
Cc: Anjan Dave <adave@vantage.com>, Dirk Lutzebäck <lutzeb@aeccom.com>, Tom Lane <tgl@sss.pgh.pa.us>, pgsql-performance@postgreSQL.org, Neil Conway <neilc@samurai.com>
Date: 2004-04-21T02:41:03Z
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