[Beowulf] Racing kernels

Tue Apr 5 05:00:54 PDT 2005

On Tue, 2005-04-05 at 06:06 -0400, Robert G. Brown wrote:most of
> what the kernel actually does is run the scheduler.  In numerical code
> the kernel can be pretty much irrelevant, as long as it isn't openly
> inefficient.  Like 99%+ of your CPU goes to the computation, no matter
> what you do tweaking the kernel.  Where kernel optimization helps is if
> the application USES parts of the kernel a LOT.  Then making small
> changes in that branch that make it run more efficient can really
> matter.

I'm with Robert on this one, the kernel doesn't actually do a lot so
it's hard to see what CPU cycles any "optimisation" are going to free
up.  Maybe the filesystem code has to do some work now and then but
choosing the right module to use here is key, not removing the ones you
aren't using.

The filesystem cache however can use a lot of memory, particularly after
the nightly "updatedb" cron session.  Much better to try and restrict
the size of your filesystem and remove all the cron entries (if ram is
an issue).

Ashley,