From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759040Ab2JYMmF (ORCPT ); Thu, 25 Oct 2012 08:42:05 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:45506 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756900Ab2JYMmE (ORCPT ); Thu, 25 Oct 2012 08:42:04 -0400 Date: Thu, 25 Oct 2012 08:40:14 -0400 From: Konrad Rzeszutek Wilk To: Jan Beulich Cc: roger.pau@citrix.com, Konrad Rzeszutek Wilk , "xen-devel@lists.xen.org" , "linux-kernel@vger.kernel.org" Subject: Re: [Xen-devel] [PATCH RFC] Persistent grant maps for xen blk drivers Message-ID: <20121025124013.GB25640@localhost.localdomain> References: <1350559321-19066-1-git-send-email-roger.pau@citrix.com> <20121022134708.GA13832@konrad-lan.dumpdata.com> <5086C0C8.5000306@citrix.com> <20121023172008.GB11787@phenom.dumpdata.com> <5086DD57.4000206@citrix.com> <20121023185049.GB20350@phenom.dumpdata.com> <5087B77A02000078000A3D00@nat28.tlf.novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5087B77A02000078000A3D00@nat28.tlf.novell.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 24, 2012 at 08:40:10AM +0100, Jan Beulich wrote: > >>> On 23.10.12 at 20:50, Konrad Rzeszutek Wilk wrote: > > On Tue, Oct 23, 2012 at 08:09:27PM +0200, Roger Pau Monné wrote: > >> On 23/10/12 19:20, Konrad Rzeszutek Wilk wrote: > >> >>>> diff --git a/drivers/block/xen-blkback/blkback.c > > b/drivers/block/xen-blkback/blkback.c > >> >>>> index c6decb9..2b982b2 100644 > >> >>>> --- a/drivers/block/xen-blkback/blkback.c > >> >>>> +++ b/drivers/block/xen-blkback/blkback.c > >> >>>> @@ -78,6 +78,7 @@ struct pending_req { > >> >>>> unsigned short operation; > >> >>>> int status; > >> >>>> struct list_head free_list; > >> >>>> + unsigned int unmap_seg[BLKIF_MAX_SEGMENTS_PER_REQUEST]; > >> > >> Should I change this to a bool? Since we are only setting it to 0 or 1. > > > > I would just keep it as 'int'. Eventually we can replace this with a > > bit-map, but that can be done later. > > I think this should be a bitmap from the beginning - why would > you want to waste 44 bytes per request for something that fits > in a single unsigned long (and the picture would get worse with > the number-of-segments extension)? > > Also - am I taking this work being done here as a silent agreement > to not invest into blkif2 to streamline the various extensions > floating around? I haven't been able (time-wise) to look at making blkif2 a possibility and I don't want to hinder this work - which provides great performance benefits.