From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836Ab1K1PYi (ORCPT ); Mon, 28 Nov 2011 10:24:38 -0500 Received: from postman.teamix.net ([194.150.191.120]:59864 "EHLO rproxy.teamix.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751291Ab1K1PYi convert rfc822-to-8bit (ORCPT ); Mon, 28 Nov 2011 10:24:38 -0500 From: Martin Steigerwald Organization: teamix GmbH To: Jens Axboe Subject: [PATCH 3/3] Mention that the util-linux package provides an ionice command. Date: Mon, 28 Nov 2011 16:24:33 +0100 User-Agent: KMail/1.13.7 (Linux/3.1.0-1-686-pae; KDE/4.6.5; i686; ; ) Cc: linux-kernel@vger.kernel.org, Vivek Goyal References: <201111281542.22258.ms@teamix.de> In-Reply-To: <201111281542.22258.ms@teamix.de> MIME-Version: 1.0 Content-Type: Text/Plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Message-Id: <201111281624.34217.ms@teamix.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Montag, 28. November 2011 schrieb Martin Steigerwald: > Hi jens und Vivek, > > Vivek, I cc'd you, cause you wrote the new cfq-iosched.txt. > > > In trying to understand how I/O priorities actually really work, I tried to > dd with > > rm nullen-id ; sync ; /usr/bin/time ionice -c3 dd if=/dev/zero of=nullen-id > count=500 bs=1M conv=fsync > > versus > > rm nullen-rl; sync ; /usr/bin/time ionice -c1 -n0 dd if=/dev/zero > of=nullen-rl count=500 bs=1M conv=fsync > > concurrently. No differences. At first I was puzzled, then I thought maybe > direct I/O makes a difference. So I tried with oflag=direct. > > And it does. > > Then I actually read the documentation block/ioprio.txt (3.1 here): > > With the introduction of cfq v3 (aka cfq-ts or time sliced cfq), basic io > > priorities are supported for reads on files. This enables users to io > > nice processes or process groups, similar to what has been possible with > > cpu scheduling for ages. This document mainly details the current > > possibilities with cfq; other io schedulers do not support io priorities > > thus far. > > According to it I/O priorities will even only work on reads. Is that > correct? I mean they do work on reads, I tested it, but *only* on reads? > > From what I see here, it also works for direct I/O write requests > > So from what I conclude is that CFQ I/O priorities work for all requests > that are issued via synchronous system calls, but not for those issued via > asynchronous calls, i. e. everything that goes through the pagecache. > > Is that correct? > > > Vivek, one thing on cfq-iosched.txt: Could slice_idle=0 make sense on SSDs? > Later on you write that there are some SSD optimizations in place that cut > down idling already. And mentioned that ionice is available from the util-linux package: >>From 182d2e06d65ea784c2bbf2e756ce0452fdebef8c Mon Sep 17 00:00:00 2001 From: Martin Steigerwald Date: Mon, 28 Nov 2011 16:16:33 +0100 Subject: [PATCH 3/3] Mention that the util-linux package provides an ionice command. --- Documentation/block/ioprio.txt | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/Documentation/block/ioprio.txt b/Documentation/block/ioprio.txt index 4775a95..5b79a29 100644 --- a/Documentation/block/ioprio.txt +++ b/Documentation/block/ioprio.txt @@ -58,6 +58,9 @@ For a running process, you can give the pid instead: will change pid 100 to run at the realtime scheduling class, at priority 2. +The util-linux package includes an ionice command that basically works like +described here. + ---> snip ionice.c tool <--- #include -- 1.7.7.3 Thanks, -- Martin Steigerwald - teamix GmbH - http://www.teamix.de gpg: 19E3 8D42 896F D004 08AC A0CA 1E10 C593 0399 AE90