From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 17 Jun 2002 02:52:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 17 Jun 2002 02:49:30 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:21006 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Mon, 17 Jun 2002 02:48:13 -0400 Message-ID: <3D0D871F.89089870@zip.com.au> Date: Sun, 16 Jun 2002 23:52:15 -0700 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.19-pre9 i686) X-Accept-Language: en MIME-Version: 1.0 To: Linus Torvalds CC: lkml , Jens Axboe Subject: [patch 8/19] go back to 256 requests per queue Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The request queue was increased from 256 slots to 512 in 2.5.20. The throughput of `dbench 128' on Randy's 384 megabyte machine fell 40%. We do need to understand why that happened, and what we can learn from it. But in the meanwhile I'd suggest that we go back to 256 slots so that this known problem doesn't impact people's evaluation and tuning of 2.5 performance. --- 2.5.22/drivers/block/ll_rw_blk.c~256-requests Sun Jun 16 22:50:18 2002 +++ 2.5.22-akpm/drivers/block/ll_rw_blk.c Sun Jun 16 23:22:46 2002 @@ -2002,8 +2002,8 @@ int __init blk_dev_init(void) queue_nr_requests = (total_ram >> 8) & ~15; /* One per quarter-megabyte */ if (queue_nr_requests < 32) queue_nr_requests = 32; - if (queue_nr_requests > 512) - queue_nr_requests = 512; + if (queue_nr_requests > 256) + queue_nr_requests = 256; /* * Batch frees according to queue length -