[CentOS] Very slow on I/O?

David King

dking at ketralnis.com
Mon Aug 21 22:06:36 UTC 2006


I seem to be having a problem with CentOS releases 4.2 and 4.3. On a  
fresh install (on two very different pieces of hardware, one Dell  
PowerEdge server and one Compaq Presario), the system seems to be  
extremely slow. It happens primarily during any hard disk I/O.

It's slow enough that my mouse skips slowly instead of moving  
smoothly, and I am unable to type. It seems to freeze for  
milliseconds at a time, which makes typing difficult because while it  
is frozen it seems to not accept keystrokes (that is, if I type the  
letter 'f' twelve times, only four of them may appear, depending on  
timing). It may be unrelated, but the clock seems to go more slowly  
during I/O as well (i.e. during times of I/O the clock runs behind  
more and more). If I were to extract a large tarball, I would have to  
wait for the while thing to finish before I could interact with the  
system at all

A simple recompile of the kernel from kernel.org sources (which, as  
you can imagine, takes quite a long time) fixes the problem entirely,  
though. So is there something that differs wildly regarding the I/O  
scheduler between the stock CentOS kernel and the stock kernel from  
kernel.org?

It would really be more convenient to be able to keep our kernel up- 
to-date automatically using the built-in packaging tools, so I hope  
that someone has seen the problem and has a work-around



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