Subject: Re: bug (trouble?) report on high mem support
To: john.helms@photomask.com (John Helms)
Date: Fri, 15 Mar 2002 20:30:22 +0000 (GMT)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), linux-kernel@vger.kernel.org,
        Jim.Trice@photomask.com (Trice Jim), Martin.Bligh@us.ibm.com
In-Reply-To: <20020315.20073100@linux.local> from "John Helms" at Mar 15, 2002 08:07:31 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Sender: linux-kernel-owner@vger.kernel.org

> Here is a top output.  We have 16Gb of ram.
> I have also tried a 2.4.9-31 enterprise=20
> kernel rpm from RedHat with the same=20
> results.

Ok that would make sense. Next question is do you have an I/O controller
that can use all the 64bit address space on the PCI bus ?

What is happening is that you are using a lot of CPU copying buffers down
into lower memory to transfer to/from disk - as well probably as that
causing a lot of competition for low memory. If your I/O controller can hit
the full 64bit space there are some rather nice test patches that should
completely obliterate the problem.

Alan
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