From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC][DATA] re "ongoing vm suckage" Date: Sun, 5 Aug 2001 21:23:57 +0100 (BST) In-Reply-To: from "Linus Torvalds" at Aug 05, 2001 01:04:29 PM MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: From: Alan Cox Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds Cc: Mike Black , Ben LaHaise , Daniel Phillips , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton List-ID: > On Sun, 5 Aug 2001, Mike Black wrote: > And quite frankly, if your disk can push 50MB/s through a 1kB > non-contiguous filesystem, then my name is Bugs Bunny. Hi Bugs 8), previously Frodo Rabbit, .. I think you watch too much kids tv 8) [To be fair I can do this through a raid controller with write back caches and the like ..] > You're more likely to have a nice contiguous file, probably on a 4kB > filesystem, and it should be able to do read-ahead of 127 pages in just a > few requests. One problem I saw with scsi was that non power of two readaheads were causing lots of small I/O requests to actual hit the disk controller (which hurt big time on hardware raid as it meant reading/rewriting chunks). I ended up seeing 128/127/1 128/127/1 128/127/1 with a 255 block queue. It might be worth logging the number of blocks in each request that hits the disk layer and dumping them out in /proc. I'll see if I still have the hack for that around. Alan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/