Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754602AbYJNJUU (ORCPT ); Tue, 14 Oct 2008 05:20:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754841AbYJNJUA (ORCPT ); Tue, 14 Oct 2008 05:20:00 -0400 Received: from hera.kernel.org ([140.211.167.34]:38394 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754847AbYJNJT7 (ORCPT ); Tue, 14 Oct 2008 05:19:59 -0400 Message-ID: <48F463C4.3070405@kernel.org> Date: Tue, 14 Oct 2008 18:17:56 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.12 (X11/20071114) MIME-Version: 1.0 To: kenneth johansson CC: Grant Grundler , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: weird throughput on write to SATA disk References: <1223925629.3947.7.camel@duo> <1223932956.3947.22.camel@duo> <1223936351.3947.41.camel@duo> <1223975694.3947.77.camel@duo> In-Reply-To: <1223975694.3947.77.camel@duo> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 14 Oct 2008 09:19:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1564 Lines: 37 kenneth johansson wrote: > On Mon, 2008-10-13 at 18:33 -0700, Grant Grundler wrote: >> On Mon, Oct 13, 2008 at 3:19 PM, kenneth johansson wrote: >> ... >>>> Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"? >>> I changed to use O_DIRECT and it's much more consistent now. 69-75 with >>> 74 about 95% of the time. >> That's low but it could be worse. Many things can contribute to slow >> disks. > Well my main problem was that it was fluctuating so much that can't be > right. > >> Favorites are overtemp (See SMART field 194) and vibration (no >> measurement possible w/o special equipment). "dd" isn't exactly a >> performance application until one uses really big block sizes (1MB or >> larger). > All my numbers comes from using 1MB blocks. but I'm not using dd. > After removing the logic that actually put some data into the buffers I > do get about 105 MB/sec using O_DIRECT. I'm doing a full disk write now > to get a reference plot. Not using O_DIRECT should be almost identical. > > >>> the disk is supposed to have 105 115 sustained >>> data rate. >> Where did 105-115 number come from? > datasheet . they listed two drives in the same column so that was not > the range it was sustained OD and the model I have max out at 105. Can you try deadline scheduler? -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/