Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751436AbVJKJ0e (ORCPT ); Tue, 11 Oct 2005 05:26:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751438AbVJKJ0e (ORCPT ); Tue, 11 Oct 2005 05:26:34 -0400 Received: from 167.imtp.Ilyichevsk.Odessa.UA ([195.66.192.167]:62698 "HELO port.imtp.ilyichevsk.odessa.ua") by vger.kernel.org with SMTP id S1751436AbVJKJ0d (ORCPT ); Tue, 11 Oct 2005 05:26:33 -0400 From: Denis Vlasenko To: Karthik Sarangan Subject: Re: AIO!! Date: Tue, 11 Oct 2005 12:25:35 +0300 User-Agent: KMail/1.8.2 Cc: Benjamin LaHaise , Linux Kernel Mailing List , Linux SCSI Mailing List References: <434A6EFC.4010100@cdac.in> <20051010160856.GI13986@kvack.org> <434B47C1.60106@cdac.in> In-Reply-To: <434B47C1.60106@cdac.in> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200510111225.35838.vda@ilport.com.ua> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1721 Lines: 52 On Tuesday 11 October 2005 08:04, Karthik Sarangan wrote: > > Benjamin LaHaise wrote: > > O_DIRECT buffers must be aligned on block sized boundaries (minimum 512 > > bytes). Check the actual return code from the aiocb and you'll find that > > it is likely -EINVAL, no -EINPROGRESS. See the man page for > > posix_memalign() to properly align the pointer. > > EEP!! I forgot all about buffer alignment!! Thanks for pointing it out Why do you constantly shout? > ------------------ > Two more questions. > > 1. Is aio_fsync of any use while 'aio_read'ing and 'aio_write'ing to > a 'raw' device or a '/dev/sdb' with O_DIRECT? I suspect you did not do some research first. > 2. I have an Ultra320 SCSI disk whose datasheet says it has a max. > possible throughput of 78MBps > > I did a 'aio_write' onto '/dev/sdb' with O_DIRECT. > Following are some throughput values. > > Buffer for IO | Avg Speed > (in KBytes) | > ----------------O----------- > Upto 512KB | 69MBps > 1024KB | 125MBps > 2048KB | 250MBps > 4096KB | 500MBps > 8192KB | 1GBps -- What the !! -- Most probably bug in your program. > Buffer cache does not come into consideration. > > Does this mean that the SCSI lower layer (aic79xx) can transfer data > only upto 512 KB? It means that you are in dire need of reading this: http://www.catb.org/~esr/faqs/smart-questions.html -- vda - 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/