Re: Fwd: kswapd issues + kernel 2.4.21-32.0.1.ELsmp

Re: Fwd: kswapd issues + kernel 2.4.21-32.0.1.ELsmp

[Robert Hancock]

Pedram M wrote:
> Hi,
> 
> I've seen this around, and have heard about it in forums and else-where,
> could somebody enlighten me with more information or with experiences
> they have had.  Looks like kswapd begins to eat CPU dramatically till the
> box eventually locks up.
> 
> Thanks,
> Pedram

Looks like an old RHEL3 kernel - first off try the latest updated kernel 
which is 2.4.21-47.0.1.EL.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

Fwd: kswapd issues + kernel 2.4.21-32.0.1.ELsmp

[Pedram M]

Hi,

I've seen this around, and have heard about it in forums and else-where,
could somebody enlighten me with more information or with experiences
they have had.  Looks like kswapd begins to eat CPU dramatically till the
box eventually locks up.

Thanks,
Pedram

Re: Fwd: kswapd issues + kernel 2.4.21-32.0.1.ELsmp

[Rik van Riel]

Pedram M wrote:
> Hi,
> 
> I've seen this around, and have heard about it in forums and else-where,
> could somebody enlighten me with more information or with experiences
> they have had.  Looks like kswapd begins to eat CPU dramatically till the
> box eventually locks up.

You'll want to contact your distro's support people, who are way
better than I am at extracting all the information needed to
debug your problem.

OTOH, chances are it's been fixed already in a more recent kernel.

-- 
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is.  Each group
calls the other unpatriotic.

Re: Fwd: kswapd issues + kernel 2.4.21-32.0.1.ELsmp

[Dan Aloni]

On Sat, Mar 31, 2007 at 01:11:29AM -0700, Pedram M wrote:
> Hi,
> 
> I've seen this around, and have heard about it in forums and else-where,
> could somebody enlighten me with more information or with experiences
> they have had.  Looks like kswapd begins to eat CPU dramatically till the
> box eventually locks up.

My experience with kswapd eating a lot of CPU tells that this particular 
problem with Linux 2.4 manifests itself on this scenario:

 * No swap is configured (we are blessed with RAM).

_AND_:

 * A lot of memory is allocated (for my case: a lot of anonymous pages 
used for applications).

Looking at this problem with kdb, I noticed that the CPU spends a lot 
of time in swap_out(), even though there are no swap devices...

So...

mm/vmscan.c, replace swap_out with this:

    static int swap_out(zone_t * classzone)
    {
            return 0;
    }

Now, this might raise some eyebrows for those MM gurus reading this
mail but I assure you I've been doing this for a lot of time (and 
a lot of machines) on 2.4.27, and it took care of my kswapd issues
quite nicely.

I hope it helps...

-- 
Dan Aloni
XIV LTD, http://www.xivstorage.com
da-x (at) monatomic.org, dan (at) xiv.co.il