Slow Disk I/O
From: Brian D. McGrew
Date: Fri May 28 2010 - 14:34:31 EST
Good morning All!
I¹m running CentOS 5.4 x86_64 on a Dell T5500 with 3GB || 12GB or RAM. I¹m
running a 2.6.18-128.el5 kernel. There is a 500GB SATA drive connected to
the onboard SATA controller. I can reproduce this problem with CentOS 5.4
i386 on the Dell T5500, T5400 and Optiplex 740¹s.
So now, on to the problem... In our software, we¹re reading in 5MP image
files in the neighborhood of 500 to 1500 files at a time. Just a simple
for() loop, open, read, close... Nothing fancy...
When I have 3GB of RAM in the system, life is good.. Each read takes 8 to
10ms... This is a good thing!
If I bump the memory up to 12GB, all of the reads are now taking 150 to
200ms.
My default, va.swappines to set to 60... If I decrease this number, the
problem gets much worse. If I up va.swappines to 100, the problem gets a
little better, but not a whole lot.
What should I be looking at???
-b
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