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





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



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