Re: Wierd context-switching issue on Xeon

When grilled further on (Thu, 29 Apr 2004 11:21:51 -0700),
Josh Berkus <josh(at)agliodbs(dot)com> confessed:

> spins_per_delay was not beneficial. Instead, try increasing them, one step
> at a time:
>
> (take baseline measurement at 100)
> 250
> 500
> 1000
> 1500
> 2000
> 3000
> 5000
>
> ... until you find an optimal level. Then report the results to us!
>

Some results. The patch mentioned is what Dave Cramer posted to the Performance
list on 4/21.

A Perl script monitored <vmstat 1> for 120 seconds and generated max and average
values. Unfortunately, I am not present on site, so I cannot physically change
the device under test to increase the db load to where it hit about 10 days ago.
That will have to wait till the 'real' work week on Monday.

Context switches - avg max

Default 7.4.1 code : 10665 69470
Default patch - 10 : 17297 21929
patch at 100 : 26825 87073
patch at 1000 : 37580 110849

Now granted, the db isn't showing the CS swap problem in a bad way (at all), but
should the numbers be trending the way they are with the patched code? Or will
these numbers potentially change dramatically when I can load up the db?

And, presuming I can re-produce what I was seeing previously (200K CS/s), you
folks want me to carry on with more testing of the patch and report the results?
Or just go away and be quiet...

The information is provided from a HP Proliant DL380 G3 with 2x 2.4 GHZ Xenon's
(with HT enabled) 2 GB ram, running 2.4.22-26mdkenterprise kernel, RAID
controller w/128 Mb battery backed cache RAID 1 on 2x 15K RPM drives for WAL
drive, RAID 0+1 on 4x 10K RPM drives for data. The only job this box has is
running this db.

Cheers,
Rob

--
21:54:48 up 2 days, 4:39, 4 users, load average: 2.00, 2.03, 2.00
Linux 2.6.5-01 #7 SMP Fri Apr 16 22:45:31 MDT 2004