From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755307AbXFXTeP (ORCPT ); Sun, 24 Jun 2007 15:34:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752512AbXFXTeB (ORCPT ); Sun, 24 Jun 2007 15:34:01 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:54137 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752332AbXFXTeA (ORCPT ); Sun, 24 Jun 2007 15:34:00 -0400 Date: Sun, 24 Jun 2007 12:33:50 -0700 From: Andrew Morton To: Patrick Mau Cc: Linux Kernel Subject: Re: [PATCH] [RFC] Adjust queue unplugging and congestion limits Message-Id: <20070624123350.edf433bc.akpm@linux-foundation.org> In-Reply-To: <20070624172722.GA865@oscar.prima.de> References: <20070624172722.GA865@oscar.prima.de> X-Mailer: Sylpheed 2.4.1 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 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 On Sun, 24 Jun 2007 19:27:23 +0200 Patrick Mau wrote: > Good afternoon > > Following is a small patch to "ll_rw_block" I played around with. > I started using "blktrace" to analyse the performance of my dated > LVM / MD / SCSI setup. It's really a nice tool, by the way. > > The changes are: > > * Change the "q->unplug_thresh" to be halve of "q->nr_requets". > This dynamically delays unplugging. It was hardcoded to 4 and > makes a difference in performace because of higher merge counts. > > * Change the unplug timeout to 10 milliseconds. > This is of course questionable, but I don't know why 3 was > choosen in the first place. I just played with it. > > * Set the congestion on/off limits further apart. > > * Cleanup the congestion checks (no "+1" anymore, more readable). > > * Update "q->unplug_thresh" whenever "q->nr_requests" is updated > through sysfs. I don't think anyone has played with these settings since they first went in and yes, there may be some benefits available here. > I did various artifical benchmarksi, mostly tar, dd and cp (also to NFS). > Comments are welcome. umm, what was the result of this benchmarking? That is rather important information ;)