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From: Roger Larsson <roger.larsson@skelleftea.mail.telia.com>
To: Adam Goldstein <Whitewlf@Whitewlf.net>
Cc: "Paweł Krawczyk" <kravietz@aba.krakow.pl>,
	"Simon Kirby" <sim@netnation.com>,
	"Adam Taylor" <iris@servercity.com>,
	linux-kernel@vger.kernel.org,
	"Sebastian Benoit" <benoit-lists@fb12.de>
Subject: Re: Very High Load, kernel 2.4.18, apache/mysql
Date: Wed, 25 Sep 2002 23:26:10 +0200	[thread overview]
Message-ID: <200209252326.10617.roger.larsson@skelleftea.mail.telia.com> (raw)
In-Reply-To: <B7E52DA4-D0C3-11D6-8C5C-000502C90EA3@Whitewlf.net>

The big question is - why that much CPU usage?

Possible answers:
* PHP, mySQL, Apache - needs that amount of CPU to perform the requested 
function.
(you have got suggestions from others)

* The implementation if either has bugs that cause the CPU usage. Garbage 
collection? Ineffective algorithms?
- Not much to do other than collecting execution profiles, quite advanced - 
recompiling of the tools will probably be needed... And probably help from 
the tools developers...

* The implementation of the user code has bugs that cause the CPU usage.
One example:
SQL SELECT with unindexed data - this can usually be noticed as buffer in load 
in vmstat but since all data fits in memory - it would cause scans in memory, 
with lots of RAM cache misses... And it would work well as long as the 
scanned data was smaller than the CPU cache?
- Suggestion: Review your index keys and select statements to make sure that 
they match!

/RogerL

  reply	other threads:[~2002-09-25 21:22 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <0EBC45FCABFC95428EBFC3A51B368C9501AF4F@jessica.herefordshire.gov.uk>
2002-09-25 20:16 ` Adam Goldstein
2002-09-25 21:26   ` Roger Larsson [this message]
2002-09-26  3:03   ` Ernst Herzberg
2002-09-26 18:36     ` Marco Colombo
2002-09-26 19:27       ` Rik van Riel
2002-09-26 20:02         ` Marco Colombo
2002-09-26 20:09           ` Rik van Riel
2002-09-26 20:25         ` Ernst Herzberg
2002-09-27  8:52       ` Martin Brulisauer
2002-10-01  5:36   ` David Rees
     [not found] <3D90FD7B.9080209@wanadoo.fr>
2002-09-25  1:12 ` Adam Goldstein
2002-09-24 23:27 Adam Goldstein
2002-09-25  0:59 ` Roger Larsson
2002-09-25  1:28   ` Rik van Riel
2002-09-25  2:38     ` Adam Goldstein
2002-09-25  5:24       ` Simon Kirby
2002-09-25  6:56         ` Adam Goldstein
2002-09-25  7:20           ` Simon Kirby
2002-09-25  7:51             ` Paweł Krawczyk
2002-09-25 13:13       ` Rik van Riel
2002-09-25 22:54       ` Jose Luis Domingo Lopez
2002-09-26 17:09       ` Joachim Breuer
2002-09-26 17:16         ` Rik van Riel
2002-09-25  3:50     ` Bernd Eckenfels
2002-09-25  3:48 ` Bernd Eckenfels

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