Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756925AbYJMVe2 (ORCPT ); Mon, 13 Oct 2008 17:34:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753817AbYJMVeS (ORCPT ); Mon, 13 Oct 2008 17:34:18 -0400 Received: from smtp-out.google.com ([216.239.33.17]:59681 "EHLO smtp-out3.google.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752425AbYJMVeS (ORCPT ); Mon, 13 Oct 2008 17:34:18 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=message-id:date:from:to:subject:cc:in-reply-to: mime-version:content-type:content-transfer-encoding: content-disposition:references; b=Yk4w4qLfHZLpGlQE04ZgF7j17dKFtqfHNr7bYh2IVqBPIsqJPQ4UpFmeVgPWo23O6 AbP3uIkDWsX0JZ7mvpX8Q== Message-ID: Date: Mon, 13 Oct 2008 14:34:00 -0700 From: "Grant Grundler" To: "kenneth johansson" Subject: Re: weird throughput on write to SATA disk Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1223932956.3947.22.camel@duo> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <1223925629.3947.7.camel@duo> <1223932956.3947.22.camel@duo> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1199 Lines: 33 On Mon, Oct 13, 2008 at 2:22 PM, kenneth johansson wrote: > On Mon, 2008-10-13 at 14:07 -0700, Grant Grundler wrote: >> On Mon, Oct 13, 2008 at 12:19 PM, kenneth johansson wrote: >> > When writing data to /dev/sdb (that is the whole disk and no filesystem) >> > it starts out ok around 100MB/sec but soon end up doing considerably >> > worse. For prolonged times lasting several minutes it hovers in the >> > 20-30MB/sec. >> >> Is the application using "O_DIRECT"? > > no just open then write no fancy stuff > >> If not, could be issue with how VM writeback is (not) working. > > the access pattern is the simplest possible. Is there any knobs I could > try to adjust. > >> Can you reproduce this using fio or even "dd"? >> (See git://git.kernel.dk/fio) > > dd is having the same effect. Can you try "dd oflag=direct if=/dev/null of=/dev/sdb bs=64k"? Or try with "sgp_dd"? It's part of sg3-utils package. thanks, grant -- 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/