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 20:36:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 24 Aug 2001 20:36:41 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:54283 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Fri, 24 Aug 2001 20:36:19 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Rik van Riel Subject: Re: [resent PATCH] Re: very slow parallel read performance Date: Sat, 25 Aug 2001 02:42:54 +0200 X-Mailer: KMail [version 1.3.1] Cc: Roger Larsson , "Marc A. Lehmann" , , In-Reply-To: In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: <20010825003625Z16138-32384+493@humbolt.nl.linux.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On August 25, 2001 01:10 am, Rik van Riel wrote: > On Sat, 25 Aug 2001, Daniel Phillips wrote: > > On August 24, 2001 09:02 pm, Rik van Riel wrote: > > > > I guess in the long run we should have automatic collapse > > > of the readahead window when we find that readahead window > > > thrashing is going on, > > > > Yes, and the most effective way to detect that the readahead > > window is too high is by keeping a history of recently evicted > > pages. > > I think it could be even easier. We simply count for each > file how many pages we read-ahead and how many pages we > read. > > If the number of pages being read-ahead is really a lot > higher than the pages being read, we know pages get evicted > before we read them ==> we shrink the readahead window. > > This simpler scheme should also be able to correctly set > the readahead window for slower data streams to smaller > than the readahead window size for faster reading data > streams (which _do_ get to use more of their data before > it is evicted again). Yes, this is a good method. -- Daniel