From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760098Ab0EDRe7 (ORCPT ); Tue, 4 May 2010 13:34:59 -0400 Received: from mail-yw0-f198.google.com ([209.85.211.198]:39516 "EHLO mail-yw0-f198.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757792Ab0EDRe6 (ORCPT ); Tue, 4 May 2010 13:34:58 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=HTza/wYrxa/xjvMok+qYJRTW6l7FvGPqHJKZmc+4RbNFrDOSpvP5hopjHD+sUYD97p 3CAL+xogBAO8YKL52cDHloBYZ9yB+6/eyXb4+5TLEc7fV3HlL18CbSR/VZTFSPsJO1I5 ITUOT3J8MKha+FAcbdDcG9jNG7n9g7VR8nmMI= MIME-Version: 1.0 In-Reply-To: References: Date: Tue, 4 May 2010 12:34:52 -0500 X-Google-Sender-Auth: 64d292c9c371dbbe Message-ID: Subject: Re: Flash IO slow 1.5 MB/s From: Paul Hartman To: Linux Kernel Mailing List Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 3, 2010 at 10:52 PM, Trenton D. Adams wrote: > It really looks like there's a scheduling issue. It seems as if the > system is IO thrashing on the flash drive, and bounces all over the > place in terms of performance. Sometimes it's really low, like the > 2.73M/s, and other times it's really fast, like the 28.86M/s. > Although you can't see it there, there were times when rsync was > registering 200kb/s. None of them are "really" accurate, as > everything is queued for writing, but the final results of 1.5M/s > (calculated from the "real" time) is terrible. I have a similar experience (posted to this list a few months ago) with mounting a flash device (mobile phone) in USB mass storage mode. When I/O scheduler for that device is CFQ, write performance is really terrible. When I change the scheduler to deadline, performance is several times better. In 2.6.32 pdflush was replaced and CFQ performance saw a 4x increase but still far too slow. CFQ in <=2.6.31: 450KB/sec CFQ in >=2.6.32: 2MB/sec Deadline in all: 17MB/sec I didn't try anything with dirty_bytes. FWIW :)