Re: Wierd context-switching issue on Xeon - Mailing list pgsql-performance

From Tom Lane
Subject Re: Wierd context-switching issue on Xeon
Date
Msg-id 13960.1082341222@sss.pgh.pa.us
Whole thread Raw
In response to Re: Wierd context-switching issue on Xeon  (Dave Cramer <pg@fastcrypt.com>)
Responses Re: Wierd context-switching issue on Xeon  (Tom Lane <tgl@sss.pgh.pa.us>)
List 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

pgsql-performance by date:

Previous
From: Tom Lane
Date:
Subject: Re: sunquery and estimated rows
Next
From: Tom Lane
Date:
Subject: Re: Wierd context-switching issue on Xeon