From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 24 Aug 2001 15:42:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 24 Aug 2001 15:42:18 -0400 Received: from islay.mach.uni-karlsruhe.de ([129.13.162.92]:14751 "EHLO mailout.plan9.de") by vger.kernel.org with ESMTP id ; Fri, 24 Aug 2001 15:42:12 -0400 Date: Fri, 24 Aug 2001 21:42:21 +0200 From: To: Roger Larsson Cc: linux-kernel@vger.kernel.org Subject: Re: [resent PATCH] Re: very slow parallel read performance Message-ID: <20010824214221.A12903@fuji.laendle> Mail-Followup-To: Roger Larsson , linux-kernel@vger.kernel.org In-Reply-To: <20010823233557.A12873@cerebro.laendle> <200108240739.f7O7dWj01330@mailc.telia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <200108240739.f7O7dWj01330@mailc.telia.com> X-Operating-System: Linux version 2.4.8-ac8 (root@cerebro) (gcc version 3.0.1) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 24, 2001 at 09:35:08AM +0200, Roger Larsson wrote: > And I found out that read ahead was too short for modern disks. That could well be, the problem in my case is that, with up to 1000 clients, I fear that there might not be enough memory for effective read-ahead (and I think read-ahead would be counter-productive even). > line is the > -#define MAX_READAHEAD 31 > +#define MAX_READAHEAD 511 I plan to try this, however, read-ahead should IMHO be zero anyway, since there simply is ot enough memory, and the kernel should not do much read-ahead when many other requests are outstanding. The real problem., however, is that read performance sinks so much when many readers run in parallel. What I need is many parallel reads because this helps the elevator scan the disk once and not jump around widely) (I have 512MB memory around 64k socket send buffer and use an additional 96k buffer currently for reading from disk, so effectively i do my own read-ahead anyway. IU just need to optimize the head movements). -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg@goof.com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |