From patchwork Tue Sep 22 10:52:08 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11792173 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9B56A59D for ; Tue, 22 Sep 2020 10:53:59 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 689CB2396D for ; Tue, 22 Sep 2020 10:53:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="eVxUdfoF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 689CB2396D Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=amazon.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kKfuk-00022f-75; Tue, 22 Sep 2020 10:52:50 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kKfuj-00022T-8s for xen-devel@lists.xenproject.org; Tue, 22 Sep 2020 10:52:49 +0000 X-Inumbo-ID: 9308aae2-8792-4aaa-9c7f-8da729ed5cb2 Received: from smtp-fw-6002.amazon.com (unknown [52.95.49.90]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 9308aae2-8792-4aaa-9c7f-8da729ed5cb2; Tue, 22 Sep 2020 10:52:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1600771969; x=1632307969; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=bgixASFZMrz4uNYz/S35PVAa/iOnwmK2jo635pLG9Ls=; b=eVxUdfoFJdps0rEuxLbaWwXotgXSK4n77TtsqLjrj30/4AQBWH5J7oFe IVAywM/NWsgQTcE8xtvXRvPlXb9oNh1qVeH9acw0IplgT7Ru1Jr6ZwLwe Y+WlNF0cOeIehP6ECmZGbdeVzQXG1faigpXSuQMUvDGrSS4/mV8/px5FI c=; X-IronPort-AV: E=Sophos;i="5.77,290,1596499200"; d="scan'208";a="55490521" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-1d-474bcd9f.us-east-1.amazon.com) ([10.43.8.6]) by smtp-border-fw-out-6002.iad6.amazon.com with ESMTP; 22 Sep 2020 10:52:48 +0000 Received: from EX13D31EUA004.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-1d-474bcd9f.us-east-1.amazon.com (Postfix) with ESMTPS id 2879EA1D05; Tue, 22 Sep 2020 10:52:45 +0000 (UTC) Received: from u3f2cd687b01c55.ant.amazon.com (10.43.162.35) by EX13D31EUA004.ant.amazon.com (10.43.165.161) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 22 Sep 2020 10:52:40 +0000 From: SeongJae Park To: , , CC: SeongJae Park , , , , , , , , Subject: [PATCH v2 2/3] xen-blkfront: add a parameter for disabling of persistent grants Date: Tue, 22 Sep 2020 12:52:08 +0200 Message-ID: <20200922105209.5284-3-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200922105209.5284-1-sjpark@amazon.com> References: <20200922105209.5284-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.162.35] X-ClientProxiedBy: EX13D14UWB003.ant.amazon.com (10.43.161.162) To EX13D31EUA004.ant.amazon.com (10.43.165.161) Precedence: Bulk X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" 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. It can be disabled from blkback side using a module parameter, 'feature_persistent'. But, it is impossible from blkfront side. For the reason, this commit adds a blkfront module parameter for disabling of the feature. [1] https://wiki.xen.org/wiki/Xen_4.3_Block_Protocol_Scalability Signed-off-by: SeongJae Park --- .../ABI/testing/sysfs-driver-xen-blkfront | 9 ++++++ drivers/block/xen-blkfront.c | 28 +++++++++++++------ 2 files changed, 29 insertions(+), 8 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkfront b/Documentation/ABI/testing/sysfs-driver-xen-blkfront index c0a6cb7eb314..9c31334cb2e6 100644 --- a/Documentation/ABI/testing/sysfs-driver-xen-blkfront +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkfront @@ -8,3 +8,12 @@ Description: is 32 - higher value means more potential throughput but more memory usage. The backend picks the minimum of the frontend and its default backend value. + +What: /sys/module/xen_blkfront/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 frontends. + The default is Y (enable). diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 91de2e0755ae..49c324f377de 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -149,6 +149,13 @@ static unsigned int xen_blkif_max_ring_order; module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, 0444); MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the shared ring"); +/* 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"); + + #define BLK_RING_SIZE(info) \ __CONST_RING_SIZE(blkif, XEN_PAGE_SIZE * (info)->nr_ring_pages) @@ -1866,11 +1873,13 @@ static int talk_to_blkback(struct xenbus_device *dev, message = "writing protocol"; goto abort_transaction; } - err = xenbus_printf(xbt, dev->nodename, - "feature-persistent", "%u", 1); - if (err) - dev_warn(&dev->dev, - "writing persistent grants feature to xenbus"); + if (feature_persistent) { + err = xenbus_printf(xbt, dev->nodename, + "feature-persistent", "%u", 1); + if (err) + dev_warn(&dev->dev, + "writing persistent grants feature to xenbus"); + } err = xenbus_transaction_end(xbt, 0); if (err) { @@ -2316,9 +2325,12 @@ static void blkfront_gather_backend_features(struct blkfront_info *info) if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0)) blkfront_setup_discard(info); - info->feature_persistent = - !!xenbus_read_unsigned(info->xbdev->otherend, - "feature-persistent", 0); + if (feature_persistent) + info->feature_persistent = + !!xenbus_read_unsigned(info->xbdev->otherend, + "feature-persistent", 0); + else + info->feature_persistent = 0; indirect_segments = xenbus_read_unsigned(info->xbdev->otherend, "feature-max-indirect-segments", 0);