Re: [PATCH 00/23] per device dirty throttling -v10

From: Tobias Oetiker <tobi@oetiker.ch>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/23] per device dirty throttling -v10
Date: Fri, 14 Sep 2007 01:13:41 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.0.999.0709140113210.8141@nyyzraq.brgvxre.pu> (raw)

Peter,

I have been using your -v9 backport to 2.6.22 (thanks very much
btw) for the last few days on an amd64 system configured like this:

 [/],[/home],[/backup],...
  on top of
 [lvm2]
  using
 [/dev/sdb]
  which is an
 [areca hw raid 6 device made up from 8 sata disks]

With your patch, performance was much improved. But still there are
some seemingly simple tasks which do not work well. Like

 cp /home/bigfile.txt /backup/bigfile.txt

or also

 rm -r /backup/big-directory

They both affect disk access times of other processes very badly.

As I said, things improved a quite a bit with your patch, but I wonder
if there is more that could be done for this particular setup?

A second thing. Since my box has 8GB memory, I am intrigued by the
idea of setting dirty_ratio not as a ratio but as an absolute
number of kilobytes as it was suggested by Neil Brown with the
dirty_kb patch a few months back. Would it make sense to forward
port this patch on top of yours ?

cheers
tobi

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
http://it.oetiker.ch tobi@oetiker.ch ++41 62 213 9902