From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752415AbbAUKOG (ORCPT ); Wed, 21 Jan 2015 05:14:06 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:45784 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750813AbbAUKN6 (ORCPT ); Wed, 21 Jan 2015 05:13:58 -0500 X-IronPort-AV: E=Sophos;i="5.09,440,1418083200"; d="scan'208";a="220136804" Message-ID: <54BF7BE4.2080005@citrix.com> Date: Wed, 21 Jan 2015 11:13:56 +0100 From: =?windows-1252?Q?Roger_Pau_Monn=E9?= User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Bob Liu , CC: , , Subject: Re: [RESEND PATCH] xen/blkfront: increase the default value of xen_blkif_max_segments References: <1421826963-6497-1-git-send-email-bob.liu@oracle.com> In-Reply-To: <1421826963-6497-1-git-send-email-bob.liu@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org El 21/01/15 a les 8.56, Bob Liu ha escrit: > The default max-segments of indirect requests was 32, so IO operations with > bigger block size(>32*4k) would be split and make performance drop. > > Nowadays backend device usually support 512k max_sectors_kb on desktop, > and usually larger on server machines connected with high-end storage system. > The default max size(128k) is not appropriate anymore, this patch increases it > to 128(128*4k=512k). > > Signed-off-by: Bob Liu Looks fine to me, the Linux backend is also prepared to handle it without any modifications. As I said in the last version, I would add the following to the commit message: This change implies we can now have 32*128+32 = 4128 in-flight grants, which greatly surpasses the default amount of persistent grants blkback can handle, so the LRU in blkback will kick in. Roger.