Re: Wierd context-switching issue on Xeon

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: pg@fastcrypt.com
Cc: lutzeb@aeccom.com, Josh Berkus <josh@agliodbs.com>, pgsql-performance@postgreSQL.org, Neil Conway <neilc@samurai.com>
Date: 2004-04-19T02:20:22Z
Lists: pgsql-performance
Dave Cramer <pg@fastcrypt.com> writes:
> So the the kernel/OS is irrelevant here ? this happens on any dual xeon?

I believe so.  The context-switch behavior might possibly be a little
more pleasant on other kernels, but the underlying spinlock problem is
not dependent on the kernel.

> What about hypterthreading does it still happen if HTT is turned off ?

The problem comes from keeping the caches synchronized between multiple
physical CPUs.  AFAICS enabling HTT wouldn't make it worse, because a
hyperthreaded processor still only has one cache.

			regards, tom lane