linux-kernel - Re: How to optimize system time for such case?

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Message-ID: <6278d2220611020127j62f94ccat5a158059feab37cb@mail.gmail.com>
Date:	Thu, 2 Nov 2006 09:27:40 +0000
From:	"Daniel J Blueman" <daniel.blueman@...il.com>
To:	zhfeng.osprey@...il.com
Cc:	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: How to optimize system time for such case?

On 02/11/06, miles <zhfeng.osprey@...il.com> wrote:
> On 11/2/06, Daniel J Blueman <daniel.blueman@...il.com> wrote:
> > FENG ZHOU wrote:
> > > Hello, all
> > > I am optimizing a compiler and I believe there is a bug in such
> > > compile. Currently, I have a test case, which is a scientific
> > > application, has a lot of system time. This is weird, because this
> > > case does not have many system calls. Meanwhile, compiled at another
> > > option, I found all the "system time" are gone! So, I assume there is
> > > some problem in the first one (though both binary produce correct
> > > result). I used some performance tuning tool and found the hottest
> > > address for CPU privilege level change event is: 0xa000000100001a70.
> > > This address is not in code or data segment. Now, I am kinda stuck
> > > here. My question is: how to find what this address is? Or find out
> > > what is the cause of the "system time"? Thanks in advance.
> > >
> > > PS: the platform is Itanium 2.
> > > -Feng
> >
> > First question is what kernel, second is how much memory?
> >
> > I recently had this experience (high system time) with some vendor
> > kernels with a system with 16GB of memory and 4-8GB processes. The VM
> > was trying to reclaim pages like crazy, but failing.
>
> The system is a debian3.1 with 2.6.8 #1 SMP kernel. The total memory is 4GB.
> Total number of processes is about 100. It is a SPEC CPU program.

I'd say it's worth a shot with a more modern kernel. There are
probably related bugs in that kernel. The one I had (related, but not
directly) problems with was 2.6.9 + vendor patches.
-- 
Daniel J Blueman
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