[rhn-users] kswapd problems

[Daniel Wittenberg]

I've been seeing the same sort of thing on one of my samba boxes, IBM
x345.  I've also been seeing huge I/O wait that can't seem to be
explained.  Over gigabit I'm only getting transfers at about 25Mb/s for
about 5 seconds and then I/O wait goes through the roof and it just sits
at about 50Mb/s.

Dan

On Wed, 2004-12-08 at 20:59 +0000, Doctor Khumalo wrote:
> I have two servers running RH Enterprise Linux (release) 3 with the latest 
> up2date patches running on kernel 2.4.21-20.ELsmp.  These are Dell PowerEdge 
> 1750 server with external Powervault 220s RAID. Both servers are 
> experiencing latency when running basic I/O commands such as scp or rsync. 
> These appear to cause kswapd to rack up an enormous amount of processor 
> resources. For example, yesterday morning, I began an scp session on each 
> server, transferring a directory with a size of 300 GB. This morning I came 
> in and found that the load average was over 500 on each server and that 
> kswapd had a CPU percentage of 198.
> 
> This has happened repeatedly over the past month.  To replicate this, I log 
> on to the first server and scp the files and directories from a file system 
> on the second server.  This is reciprocated by running an scp process for 
> files and directories from a file system the first server.  Both file 
> systems are on /dev/sdb, an external RAID box, and are over 300 GB. Both 
> servers are on the same Gigabit network.
> 
> The files transfer at approximately 15 GB an hour until about eight hours 
> into the job when it begins to slow down to about 4-5 GB an hour and the 
> load average increases over 200. It is at this point that kswapd begins to 
> go through the roof while ssh and scp use relatively little resources 
> (according to top and ps wauxg).
> 
> After I kill the scp job, about 20 hours into it, kswapd continues to use 
> the same amount of resources.
> 
> I have done this CPU hyper threading enabled and disabled with no 
> improvement.
> 
> Anyone ever experienced this before?
> 
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-- 
======================
Daniel Wittenberg
RHCE
President/CTO
The Starken Group Ltd.
http://www.starken.com