[Linux-cluster] Re: D Apache processes

[Axel Thimm]

On Mon, Dec 06, 2004 at 06:52:02PM -0800, Duncan Morgan wrote:
> Hello,
> 
> We have apache running on 14 GFS nodes where the web roots are shared
> via GFS. Occasionally we see that the load on all nodes rises
> dramatically (to 150+) and all httpd processes become dead (D). I know
> this is a little lacking in details but does anyone have any insight
> into this? We suspected perhaps a cron job was running simultaneously
> against the GFS file system on all nodes but have virtually ruled this
> out.

I am getting the same behaviour on a non-clustered, non GFS system
(dual opteron on FC2/x86_64). There is a peak of almost all httpd
processes in D-state (that's not really dead, but "uninterruptible
sleep", e.g. when the kernel does IO for the userland process). A few
seconds later the number of D-processes fall down to less than a dozen
and you can watch your load exponentially decrease.

Note that 150 is the default MaxClient setting for apache, that's why
you get slightly more than 150 load.

I guess that's a kernel issue with too many processes accessing the
same files. Nothing to do directly with GFS.

> Please help - this is very alarming.
> 
> Thanks in advance,
> Duncan Morgan
> 

-- 
Axel.Thimm at ATrpms.net
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