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=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 B2D80C433DF for ; Wed, 29 Jul 2020 04:10:16 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 65BC420768 for ; Wed, 29 Jul 2020 04:10:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Xo6GnrGP"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="OH1QkGNd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65BC420768 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:Reply-To:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vchKM8Fku1gLn5E/gX9FTtYHojBPIHqaPqzGze2ubE4=; b=Xo6GnrGPn5hDyhceoA4gbYzFok 3KN5z/rlObChutSRLR/AoNW5exFnNLsXsb5vr4EjoLdq+6O5qEa4sr2Vxk3Pjofcf5fk4uoOUHkUz h7DwR25FJlmL9L32id/ZMyxc4JYOfk9tk0dO5+Q7c+VfXZVEb0kab1IIqBMF/K7sMc3e8cgf46qPB N4/k1q92TeNPzIWQ1Pr5Gf7A4EvJbHhjbc+wLzRpBMKexAyqSHHqp16qO7xM7EbkCPYJIEpbpKkTN HbrylrDknybClmRfiVNA/ieB2oerZEzu+1uwJEscroS9BJLa3avrk5VXAxwFmWqL0NlK1RXwW7oy6 tWF6d+/g==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k0dPr-0006lR-G7; Wed, 29 Jul 2020 04:10:07 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k0dPq-0006ky-2r for linux-nvme@lists.infradead.org; Wed, 29 Jul 2020 04:10:06 +0000 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EA2C9206D7; Wed, 29 Jul 2020 04:10:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595995805; bh=IKuBNsl4qI263D75wzMMfJxggGK+N6Re79brmEIzMxA=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=OH1QkGNd8OQvbYtYzMt3W9axgOV4KN7144XsAoavF/F84RBlHJJIG75jz/4fq06/Y H347LXh6xgmmQ4rxh0sKnPuqwkgbQGfj+7P7BQFfpaFdX76IwSDQlUcNDQmUxelGKk UM3Go1sN/Nzwhz6ROLO3/Uy3rpGwcDvhQg/VfWjw= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id C7F783522621; Tue, 28 Jul 2020 21:10:04 -0700 (PDT) Date: Tue, 28 Jul 2020 21:10:04 -0700 From: "Paul E. McKenney" To: Sagi Grimberg Subject: Re: [PATCH v5 1/2] blk-mq: add tagset quiesce interface Message-ID: <20200729041004.GV9247@paulmck-ThinkPad-P72> References: <20200727231022.307602-1-sagi@grimberg.me> <20200727231022.307602-2-sagi@grimberg.me> <20200728071859.GA21629@lst.de> <20200728091633.GB1326626@T590> <20200728135436.GP9247@paulmck-ThinkPad-P72> <20200729003124.GT9247@paulmck-ThinkPad-P72> <07c90cf1-bb6f-a343-b0bf-4c91b9acb431@grimberg.me> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <07c90cf1-bb6f-a343-b0bf-4c91b9acb431@grimberg.me> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200729_001006_246294_C488182D X-CRM114-Status: GOOD ( 22.29 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: paulmck@kernel.org Cc: Jens Axboe , linux-nvme@lists.infradead.org, Ming Lei , linux-block@vger.kernel.org, Chao Leng , Keith Busch , Ming Lin , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Jul 28, 2020 at 05:43:02PM -0700, Sagi Grimberg wrote: > > > > Dynamically allocating each one is possible but not very scalable. > > > > > > The question is if there is some way, we can do this with on-stack > > > or a single on-heap rcu_head or equivalent that can achieve the same > > > effect. > > > > If the hctx structures are guaranteed to stay put, you could count > > them and then do a single allocation of an array of rcu_head structures > > (or some larger structure containing an rcu_head structure, if needed). > > You could then sequence through this array, consuming one rcu_head per > > hctx as you processed it. Once all the callbacks had been invoked, > > it would be safe to free the array. > > > > Sounds too simple, though. So what am I missing? > > We don't want higher-order allocations... OK, I will bite... Do multiple lower-order allocations (page size is still lower-order, correct?) and link them together. Sorry, couldn't resist... Thanx, Paul _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme