[Centos] Re: kernel question

Tue Sep 21 18:26:26 UTC 2004
Bart Schaefer <schaefer+centos at zanshin.com>

William Warren wrote:

> An interesting bug in RHEL 3(which affects CentOS 3) has been 
> bantered around for a while.  There are some kernel 
> patches(beyond my scope right now) or some echo statements tht 
> are used(this helped my situation).

>    https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=89226

I don't have any direct feedback on Warren's [not excerpted] question 
about using other kernels, but I have some feedback on the echo statements 
that he mentions.

I had been noticing that memory-intensive apps such as Mozilla were taking 
a very long time to swap back in after having been idle overnight -- more 
than a couple of minutes, often, when I would switch desktops for the 
first time each day to the one where I keep Moz running, before the window
would refresh.

Scanning through the bugzilla report, I saw the kernel patch that changes
the vm.pagecache defaults.  So I executed

	echo "1 5 10" > /proc/sys/vm/pagecache

My applications are now MUCH more responsive; there's never a delay before 
the Mozilla window refreshes, and VMware works noticeably better.  If you
are running CentOS 3.1 or RHEL3, you might want to try this, even if you
aren't seeing serious problems with swapping.

This brings me to two questions:

(1) Is the aforementioned kernel patch already present in the CentOS-3.3

(2) (Somwhat OT) Is there an equivalent pagecache tweak for RedHat 9?  The
    /proc/sys/vm/pagecache "device" is not present in RH9.