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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 84E52C4332F for ; Mon, 17 Oct 2022 13:42:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=wx3Izz00mSsl5ykG4rVsXiSmWEQqB2Hvu6El7feFXVM=; b=WFBvlpm7kKZeaiNoplCX75glJy CQUFoLzQQyCKQPfc5o+Vw6noSBAfh/sBTW304EedfqHlzKKeDmLsC5O4MFeU1bO+brDmcRiuwbyUR Fvz/hWEpFt2P+B54iuDFqfubrw599n3GXawxVurH3RpfS/OCPr0WjcTQAiMLVlpRPL9oCsPRWTBAL 6/F4uLSWf4lXAazDCrv0dpylq5jIOVozYZxD8QUGQ8rBxamZNYYdbRSilJi6mVpLwlhxNy6m9klFa UABHSQ/pVO0L0o+Ld3Hl37fFhnREbSoTWbZNr7Hxx/Okh62IbNYVBIyC8kexLz615cSckxZfjOJj4 ayfPZvvg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1okQOJ-00CD0z-29; Mon, 17 Oct 2022 13:42:51 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1okQOG-00CCuo-C3 for linux-nvme@lists.infradead.org; Mon, 17 Oct 2022 13:42:49 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id AE02868BFE; Mon, 17 Oct 2022 15:42:44 +0200 (CEST) Date: Mon, 17 Oct 2022 15:42:44 +0200 From: Christoph Hellwig To: Chao Leng Cc: linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, hch@lst.de, sagi@grimberg.me, kbusch@kernel.org, ming.lei@redhat.com, axboe@kernel.dk, "Paul E. McKenney" Subject: Re: [PATCH v2 1/2] blk-mq: add tagset quiesce interface Message-ID: <20221017134244.GA24775@lst.de> References: <20221013094450.5947-1-lengchao@huawei.com> <20221013094450.5947-2-lengchao@huawei.com> <20221017133906.GA24492@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221017133906.GA24492@lst.de> User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221017_064248_579045_80892C87 X-CRM114-Status: GOOD ( 14.14 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Mon, Oct 17, 2022 at 03:39:06PM +0200, Christoph Hellwig wrote: > Having to allocate a struct rcu_synchronize for each of the potentially > many queues here is a bit sad. > > Pull just explained the start_poll_synchronize_rcu interfaces at ALPSS > last week, so I wonder if something like that would also be feasible > for SRCU, as that would come in really handy here. Alternatively I wonder if we could simply use a single srcu_struct in the tag_set instead of one per-queue. That would potentially increase the number of read side critical sections blk_mq_wait_quiesce_done would have to wait for in tagsets with multiple queues, but I wonder how much overhead that would be in practive.