From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E131CC4363D for ; Tue, 22 Sep 2020 14:26:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DB4B20C09 for ; Tue, 22 Sep 2020 14:26:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="m0iLyt7i" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726605AbgIVO0A (ORCPT ); Tue, 22 Sep 2020 10:26:00 -0400 Received: from mx2.suse.de ([195.135.220.15]:34962 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726507AbgIVO0A (ORCPT ); Tue, 22 Sep 2020 10:26:00 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1600784758; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=m55LpYIPz2/gLR7XJJbmS3D3fw3yA3M+76SUekukJQk=; b=m0iLyt7iNT74lbvJnYoorfut2vAzNlJWmpgI3g8z8olHVRy7M4zUcJIm0uyB/KSHHY53JR kRGyxfTp56noVOvVliW4GFTKSB8DG7W4jGQlFBY/tc74I14diYmS6Cok3KLioMRe1PaT9m UwoTjhai2MFkTtZlUXqyNuLYslIA4BY= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 28970ACC2; Tue, 22 Sep 2020 14:26:35 +0000 (UTC) Subject: Re: [PATCH v3 1/3] xen-blkback: add a parameter for disabling of persistent grants To: SeongJae Park , konrad.wilk@oracle.com, roger.pau@citrix.com Cc: SeongJae Park , axboe@kernel.dk, aliguori@amazon.com, amit@kernel.org, mheyne@amazon.de, pdurrant@amazon.co.uk, linux-block@vger.kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org References: <20200922141549.26154-1-sjpark@amazon.com> <20200922141549.26154-2-sjpark@amazon.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <5d0f75f1-636e-e485-c616-bca47bd6932f@suse.com> Date: Tue, 22 Sep 2020 16:25:57 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200922141549.26154-2-sjpark@amazon.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 22.09.20 16:15, SeongJae Park wrote: > From: SeongJae Park > > Persistent grants feature provides high scalability. On some small > systems, however, it could incur data copy overheads[1] and thus it is > required to be disabled. But, there is no option to disable it. For > the reason, this commit adds a module parameter for disabling of the > feature. > > [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability > > Signed-off-by: Anthony Liguori > Signed-off-by: SeongJae Park > --- > .../ABI/testing/sysfs-driver-xen-blkback | 9 ++++++++ > drivers/block/xen-blkback/xenbus.c | 22 ++++++++++++++----- > 2 files changed, 25 insertions(+), 6 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback > index ecb7942ff146..ac2947b98950 100644 > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback > @@ -35,3 +35,12 @@ Description: > controls the duration in milliseconds that blkback will not > cache any page not backed by a grant mapping. > The default is 10ms. > + > +What: /sys/module/xen_blkback/parameters/feature_persistent > +Date: September 2020 > +KernelVersion: 5.10 > +Contact: SeongJae Park > +Description: > + Whether to enable the persistent grants feature or not. Note > + that this option only takes effect on newly created backends. > + The default is Y (enable). > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > index b9aa5d1ac10b..f4c8827fa0ad 100644 > --- a/drivers/block/xen-blkback/xenbus.c > +++ b/drivers/block/xen-blkback/xenbus.c > @@ -474,6 +474,12 @@ static void xen_vbd_free(struct xen_vbd *vbd) > vbd->bdev = NULL; > } > > +/* Enable the persistent grants feature. */ > +static bool feature_persistent = true; > +module_param(feature_persistent, bool, 0644); > +MODULE_PARM_DESC(feature_persistent, > + "Enables the persistent grants feature"); > + > static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > unsigned major, unsigned minor, int readonly, > int cdrom) > @@ -519,6 +525,8 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > if (q && blk_queue_secure_erase(q)) > vbd->discard_secure = true; > > + vbd->feature_gnt_persistent = feature_persistent ? 1 : 0; Just assign the value instead of using the ternary operator? With that changed you can add my Reviewed-by: Juergen Gross Juergen