From patchwork Wed Sep 23 06:18:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 11794047 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 31886112C for ; Wed, 23 Sep 2020 06:19:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 159CF21D43 for ; Wed, 23 Sep 2020 06:19:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="c5Oa9jDD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726647AbgIWGTX (ORCPT ); Wed, 23 Sep 2020 02:19:23 -0400 Received: from smtp-fw-33001.amazon.com ([207.171.190.10]:21096 "EHLO smtp-fw-33001.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbgIWGTW (ORCPT ); Wed, 23 Sep 2020 02:19:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1600841963; x=1632377963; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=qIdI2Ar+FjlI0h5NCqVRr5Ean1G5IGrdck+ZoSf7G0w=; b=c5Oa9jDDccuvfyfRuSH9Krksx/ZUvGQ0gBmDj5i+/RIflRz8g4nx+eSJ tNB6BALvyelgRch8RKsyFiUTg7oGHcCQDZiT9reJGpGHbgFwofaoKj/IG v3EM8/CzQQ8PnXJ4jArHlwOEt2/4fe+qyn3TSWXwf/ZwlyVhF53ZBM1rm k=; X-IronPort-AV: E=Sophos;i="5.77,293,1596499200"; d="scan'208";a="77284083" Received: from sea32-co-svc-lb4-vlan3.sea.corp.amazon.com (HELO email-inbound-relay-2a-e7be2041.us-west-2.amazon.com) ([10.47.23.38]) by smtp-border-fw-out-33001.sea14.amazon.com with ESMTP; 23 Sep 2020 06:19:14 +0000 Received: from EX13D31EUA004.ant.amazon.com (pdx4-ws-svc-p6-lb7-vlan2.pdx.amazon.com [10.170.41.162]) by email-inbound-relay-2a-e7be2041.us-west-2.amazon.com (Postfix) with ESMTPS id B2778A1DEE; Wed, 23 Sep 2020 06:19:12 +0000 (UTC) Received: from u3f2cd687b01c55.ant.amazon.com (10.43.162.85) by EX13D31EUA004.ant.amazon.com (10.43.165.161) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 23 Sep 2020 06:19:06 +0000 From: SeongJae Park To: , , CC: SeongJae Park , , , , , , , , Subject: [PATCH v4 1/3] xen-blkback: add a parameter for disabling of persistent grants Date: Wed, 23 Sep 2020 08:18:39 +0200 Message-ID: <20200923061841.20531-2-sjpark@amazon.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200923061841.20531-1-sjpark@amazon.com> References: <20200923061841.20531-1-sjpark@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.162.85] X-ClientProxiedBy: EX13D10UWB001.ant.amazon.com (10.43.161.111) To EX13D31EUA004.ant.amazon.com (10.43.165.161) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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 Reviewed-by: Juergen Gross Acked-by: Roger Pau Monné --- .../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..8fc34211dc8b 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; + pr_debug("Successful creation of handle=%04x (dom=%u)\n", handle, blkif->domid); return 0; @@ -906,7 +914,8 @@ static void connect(struct backend_info *be) xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support); - err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1); + err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", + be->blkif->vbd.feature_gnt_persistent); if (err) { xenbus_dev_fatal(dev, err, "writing %s/feature-persistent", dev->nodename); @@ -1067,7 +1076,6 @@ static int connect_ring(struct backend_info *be) { struct xenbus_device *dev = be->dev; struct xen_blkif *blkif = be->blkif; - unsigned int pers_grants; char protocol[64] = ""; int err, i; char *xspath; @@ -1093,9 +1101,11 @@ static int connect_ring(struct backend_info *be) xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol); return -ENOSYS; } - pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent", - 0); - blkif->vbd.feature_gnt_persistent = pers_grants; + if (blkif->vbd.feature_gnt_persistent) + blkif->vbd.feature_gnt_persistent = + xenbus_read_unsigned(dev->otherend, + "feature-persistent", 0); + blkif->vbd.overflow_max_grants = 0; /* @@ -1118,7 +1128,7 @@ static int connect_ring(struct backend_info *be) pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename, blkif->nr_rings, blkif->blk_protocol, protocol, - pers_grants ? "persistent grants" : ""); + blkif->vbd.feature_gnt_persistent ? "persistent grants" : ""); ring_page_order = xenbus_read_unsigned(dev->otherend, "ring-page-order", 0);