From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Hardy Subject: Re: Software RAID & Filesystem Cache Date: Thu, 05 Aug 2004 10:49:14 -0700 Sender: linux-raid-owner@vger.kernel.org Message-ID: <4112731A.5030000@h3c.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: "'linux-raid@vger.kernel.org'" List-Id: linux-raid.ids Philip Molter wrote: > Mike Hardy wrote: > [ ... snip ... ] >> The readahead is the first place I'd look though. All in all, it >> appears that 2.6 kernels need a great deal more I/O tuning before they >> can be put in production. While I like the flexibility that's >> available, the default settings seem to be a major negative change >> from 2.4. This sort of thing is just now being quantified and >> hopefully it gets sorted out in the next couple of releases > > > [ .. snip ... ] > > My first suspicion was readahead as well, but I couldn't find any of the > sysctl options to control readahead in the kernel (as there were under I'm honestly not trying to be a smart-ass by posting this since I haven't played with these *a single bit* - however, this was what I found: /sys % find . | grep ahead ./block/hdf/queue/read_ahead_kb ./block/hdg/queue/read_ahead_kb ./block/hdc/queue/read_ahead_kb ./block/hda/queue/read_ahead_kb Maybe those are the appropriate knobs to twiddle? If so, it appears they've gone per-device, and they've moved to sysfs... -Mike