From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 26 Aug 2001 09:22:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 26 Aug 2001 09:22:10 -0400 Received: from islay.mach.uni-karlsruhe.de ([129.13.162.92]:436 "EHLO mailout.plan9.de") by vger.kernel.org with ESMTP id ; Sun, 26 Aug 2001 09:21:56 -0400 Date: Sun, 26 Aug 2001 15:22:04 +0200 From: To: Rik van Riel Cc: Daniel Phillips , Alan Cox , Roger Larsson , linux-kernel@vger.kernel.org Subject: Re: [resent PATCH] Re: very slow parallel read performance Message-ID: <20010826152204.B22677@cerebro.laendle> Mail-Followup-To: Rik van Riel , Daniel Phillips , Alan Cox , Roger Larsson , linux-kernel@vger.kernel.org In-Reply-To: <20010826013155Z16205-32383+1383@humbolt.nl.linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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 Sun, Aug 26, 2001 at 12:32:09AM -0300, Rik van Riel wrote: > Reality check time indeed. If you propose that disabling > readahead should improve read performance something fishy > is going on ;) Actually, I also believe that. If you have no memory to store read-ahead data then your only chance is what I try to do: massively parallelize reads so the elevator can optimize what's possible and do no read-ahead whatsoever. Of course, in general, read-ahead is a must. Using 256k socket buffer + 128k userspace bounce buffer is, effectively, a 384k read-ahead per connenction (the average connection speed is about 8k/s btw, so thats about one read every 16 seconds. 16 seconds is also about the time between sending out the response headers and the beginning of the data transfer, which is ok in my case). The problem is that read-ahead (seems to) go completely havoc when read()'s are issued in many threads at the same time. -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg@goof.com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |