From mboxrd@z Thu Jan 1 00:00:00 1970 From: kenneth johansson Subject: Re: weird throughput on write to SATA disk Date: Mon, 13 Oct 2008 23:22:36 +0200 Message-ID: <1223932956.3947.22.camel@duo> References: <1223925629.3947.7.camel@duo> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from 1-1-4-20a.ras.sth.bostream.se ([82.182.72.90]:45427 "EHLO amd.kenjo.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756004AbYJMVWj (ORCPT ); Mon, 13 Oct 2008 17:22:39 -0400 In-Reply-To: Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Grant Grundler Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org 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.