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Re: CPU overhead when handling large files?

To: stimits@xxxxxxxxx
Subject: Re: CPU overhead when handling large files?
From: Jean Francois Martinez <jfm2@xxxxxxxxxxxxxxxx>
Date: 23 Jan 2003 13:49:11 +0100
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <3E29FF4F.2000809@xxxxxxxxx>
References: <1042910194.2187.15.camel@xxxxxxxxxxxxxxxxxxxx> <3E29FF4F.2000809@xxxxxxxxx>
Sender: linux-xfs-bounce@xxxxxxxxxxx
On Sun, 2003-01-19 at 02:28, D. Stimits wrote:
> Seung-yeong Oh wrote:
> 
> > Hello,
> > Originally, I installed RedHat7.2 + SGI XFS 1.0.2.
> > I now have fully updated RedHat7.2 + SGI XFS 1.2pre5 (rebuilt kernel RPM
> > to be installed on RedHat 7.x).
> > For current seup, I'm wondering if the following behavior is normal;
> > When handling large files, for example, copying a few 700MB files from
> > one directory to another, at some point in the middle of the process or
> > at the end of it, the process hangs for several minutes taking up 99% of
> > CPU.
> > A friend of mine told me it might take some time to rewrite inodes as
> > it's a journaling file system, but I don't remember the XFS acted this
> > way before when I was using 1.0.2 of it. And 1.1 for that matter...
> > I'd appreciate any input. Thank you.
> > Have a nice weekend.
> >
> FYI, if you use IDE drives, and do not have UDMA on, it will always use 
> tons of cpu power to do copies, no matter what filesystem.
> 

A few years ago I had a disk who used 97% of the CPU when doing 
a "dd if=/dev/hda of=/dev/null bs=8192".  CPU usage dropped to under
20% after enabling DMA.  Throughput was nearly trebled.

This was a DMA not UDMA disk.


                                JFM


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