Re: kswapd taking 100% CPU - only there's no swap?

[Don MacAskill <don smugmug com>]

Stephen J. Smoogen wrote:

> Could be lots of reasons.. a lot more info would be needed to answer it:
>
> What is your CPU

Opteron 875

>   Is it 32 bit or 64 bit

64 bit, running 64bit RHEL4 AS

>   How many do you have

4 of them (2 cores each, for a total of 8 cores)

>   How much CPU cache do they have

1MB / core, I think?

>   How does this particular architecture deal with more than X ram (NUMA, etc)

Opterons have integrated memory controllers, and I think the RHEL4 
kernels treat them as NUMA architectures.  I could be wrong - we're 
getting out of my depth here.

>   How large are the processes that you are dealing with (1 gig, 3 gig, larger?)

A single mysqld using ~27-28GB.

>   How large does this particular architecture deal with X amount of
> ram allocated to a process?

Good question.

However, it should be noted that for many many months, this same 
hardware running this same software didn't have this problem.  Only 
after upgrading kernels (I'm 99% sure this is what caused it, and other 
reports online for both RHEL4 and CentOS seem to confirm) am I seeing 
this issue.

> > I don't want any disk activity.  I have ample RAM (32GB, of which I
> > leave >3GB free at all times).
> >
> > I have plenty of diskless boxes which obviously have no swap.  Are you
> > saying that I can't/shouldn't run diskless either?
>
> I think you are putting words in Arjan's mouth here.. Arjan doesnt
> work for Red Hat and is trying to be helpful for you.

No, sorry, I think I'm being misunderstood.  I don't know if Arjan works 
for RedHat now, but clearly he did - and in an important position on the 
RH kernel (maintainer, I believe?).

I'm asking him as someone with far more knowledge and expertise than I 
have - not as someone who speaks officially for Red Hat.

Don