Horton

Re: Wierd context-switching issue on Xeon

Magnus Naeslund(t) <mag@fbab.net>

View thread
From: "Magnus Naeslund(t)" <mag@fbab.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: josh@agliodbs.com, Joe Conway <mail@joeconway.com>, "scott.marlowe" <scott.marlowe@ihs.com>, Bruce Momjian <pgman@candle.pha.pa.us>, lutzeb@aeccom.com, pgsql-performance@postgresql.org, Neil Conway <neilc@samurai.com>
Date: 2004-04-20T22:47:49Z
Lists: pgsql-performance

Attachments

Tom Lane wrote:
> 
> Hmmm ... I've been able to reproduce the CS storm on a dual Athlon,
> which seems to pretty much let the Xeon per se off the hook.  Anybody
> got a multiple Opteron to try?  Totally non-Intel CPUs?
> 
> It would be interesting to see results with non-Linux kernels, too.
> 
> 			regards, tom lane

I also tested on an dual Athlon MP Tyan Thunder motherboard (2xMP2800+, 
2.5GB memory), and got the same high numbers.
I then ran with kernel 2.6.5, it lowered them a little, but it's still 
some ping pong effect here. I wonder if this is some effect of the 
scheduler, maybe the shed frequency alone (100HZ vs 1000HZ).

It would be interesting to see what a locking implementation ala FUTEX 
style would give on an 2.6 kernel, as i understood it that would work 
cross process with some work.

The first file attached is kernel 2.4 running one process then starting 
up the other one.
Same with second file, but with kernel 2.6...

Regards
Magnus