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[130.117.225.111]) by mx.google.com with ESMTPS id ffacd0b85a97d-48e3ed04f49si32773880f8f.304.2026.10.29.07.08.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Oct 2026 07:08:14 -0700 (PDT) Received-SPF: pass (google.com: domain of andrey.zhadchenko@virtuozzo.com designates 130.117.225.111 as permitted sender) client-ip=130.117.225.111; Authentication-Results: mx.google.com; dkim=pass header.i=@virtuozzo.com header.s=relay header.b=AYEs2l0Z; spf=pass (google.com: domain of andrey.zhadchenko@virtuozzo.com designates 130.117.225.111 as permitted sender) smtp.mailfrom=andrey.zhadchenko@virtuozzo.com; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=virtuozzo.com DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=MIME-Version:Message-ID:Date:Subject:From: Content-Type; bh=3AhOLHwHcUrncWXvPuz0E0RzDWVJ1bU1yYFfNJxXCO8=; b=AYEs2l0Z+alt rO/o3A0F19cl1utYuZy0ZKh0P+Ox5O3KOUMd+L2heaQyBLrkwqMFPE+qHpR9jei4MzNUJ5dg0ifQE bOh2fzeQkQr1ZebrrJGDVn7YIkK5ol9MAOhH12873JEwBSC0Wrak5ZqLXOTKCOISY+6mmFgBxVH4q Nl0mXA9a40U34eDy21r4wyu9Sbola8J9V8iXU5gfkpHi9WYVACON437omDZyinLgHAByb0Qj3lKdX /27/x56V62Ov9Oa1wMDMi1xjZg/z1Bf0qQ+aouAFAMZN8vvOivflfA2XvbYYPj/6/C+YKGPLtdjbd fyJqDFCYfZ0YQ9dUyktPlQ==; Received: from [130.117.225.5] (helo=vz9-demens-1.aci.vzint.dev) by relay.virtuozzo.com with esmtp (Exim 4.96) (envelope-from ) id 1xMQjq-006pKz-02; Thu, 29 Oct 2026 15:08:11 +0100 From: Andrey Zhadchenko To: ptikhomirov@virtuozzo.com, alexander.ivanov@virtuozzo.com Date: Thu, 29 Oct 2026 17:03:45 +0300 Message-ID: <20261029140346.465768-7-andrey.zhadchenko@virtuozzo.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20261029140346.465768-1-andrey.zhadchenko@virtuozzo.com> References: <20261029140346.465768-1-andrey.zhadchenko@virtuozzo.com> MIME-Version: 1.0 X-OZ-Fwd: true Cc: devel@openvz.org Subject: [Devel] [PATCH hci-8.1 6/7] drivers/md/dm-qcow2: declare DM_TARGET_NOWAIT X-BeenThere: devel@openvz.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: OpenVZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: devel-bounces@openvz.org Errors-To: devel-bounces@openvz.org dm-qcow2 is a request-based target: REQ_NOWAIT handling is done by blk-mq (tag allocation) before a request reaches us, and clone_and_map_rq() never blocks. Still, the target does not declare DM_TARGET_NOWAIT, so dm_table_set_restrictions() clears BLK_FEAT_NOWAIT on the mapped device and the block device file gets no FMODE_NOWAIT. As a result io_uring is unable to issue I/O in nowait mode and punts *every* request to io-wq worker threads: on 4k randwrite (io_uring, qd=64, 4 jobs) io-wq threads burn ~24% of all cpus doing nothing but a thread handoff. before after qd=64 nj=4 IOPS 1034K (11% idle) 892K (30% idle) qd=1 nj=1 lat 8us 6us The lower nj=4 number is because io-wq threads were providing "free" parallelism for the single-cpu submitters; the next patch gets it back without burning the cpus. https://virtuozzo.atlassian.net/browse/VSTOR-95494 Feature: dm-qcow2: block device over QCOW2 files driver Signed-off-by: Andrey Zhadchenko --- drivers/md/dm-qcow2-target.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c index be09615eb8e2e..4b9ae86ac9443 100644 --- a/drivers/md/dm-qcow2-target.c +++ b/drivers/md/dm-qcow2-target.c @@ -1159,7 +1159,7 @@ static void qcow2_resume(struct dm_target *ti) static struct target_type qcow2_target = { .name = "qcow2", .version = {1, 0, 0}, - .features = DM_TARGET_SINGLETON, + .features = DM_TARGET_SINGLETON | DM_TARGET_NOWAIT, .module = THIS_MODULE, .ctr = qcow2_ctr, .dtr = qcow2_dtr, -- 2.43.5 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel