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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 F050CC433E5 for ; Mon, 27 Jul 2020 05:56:15 +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 BFA34207BB for ; Mon, 27 Jul 2020 05:56:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="TxLIKyMH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFA34207BB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com 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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=41BiwdWxY5YNxP+szh+27No1sUx271LLP/4VBvcZuqA=; b=TxLIKyMH71uxpH/8f8aYhGFKB tQ2kfFIVivbJS6ESIx3fDzYpZZnkvitLpH0r+B3bTHf8PbH6mIARsuR/smdbW5uvdbUXwPQBvTrM6 yabuKrEtfjoSzNvRG87edOcPNb6sZLmQx2veeGgzIO5+AyYjgm3s79aEbTGkfqIElZwdEPYZDDhE2 i8ydAe+by1jAi0x93PhNqWKHJGi83icSYTMYnBtRgVMzYfOx/GwYt2XuGK7Y3OCNrEUoGFxpUeFXM RGgmMKtohPyxAeWYpQ1B1AZrKv3+KHZSEiKSIFQkRupFMrr9EIQOfv1xGwL/F4+KCXbHpbpwQY6VH D5f7xNLIg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jzw7L-0006Qh-P0; Mon, 27 Jul 2020 05:56:07 +0000 Received: from szxga06-in.huawei.com ([45.249.212.32] helo=huawei.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jzw7I-0006JC-5L for linux-nvme@lists.infradead.org; Mon, 27 Jul 2020 05:56:05 +0000 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 2C129B3B47A385A0E7F0; Mon, 27 Jul 2020 13:55:54 +0800 (CST) Received: from [10.27.125.30] (10.27.125.30) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Mon, 27 Jul 2020 13:55:53 +0800 Subject: Re: [PATCH v3 1/2] blk-mq: add async quiesce interface To: Ming Lei References: <20200726002301.145627-1-sagi@grimberg.me> <20200726002301.145627-2-sagi@grimberg.me> <20200726093132.GD1110104@T590> <9ac5f658-31b3-bb19-e5fe-385a629a7d67@grimberg.me> <20200727020803.GC1129253@T590> <20200727035033.GD1129253@T590> From: Chao Leng Message-ID: <79ab699e-3f50-26c0-3c85-1962ae4dedac@huawei.com> Date: Mon, 27 Jul 2020 13:55:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200727035033.GD1129253@T590> Content-Language: en-US X-Originating-IP: [10.27.125.30] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200727_015604_455576_0A54DEEC X-CRM114-Status: GOOD ( 11.51 ) 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: , Cc: Jens Axboe , Sagi Grimberg , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Keith Busch , Christoph Hellwig Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 2020/7/27 11:50, Ming Lei wrote: > On Mon, Jul 27, 2020 at 11:33:43AM +0800, Chao Leng wrote: >> >> >> On 2020/7/27 10:08, Ming Lei wrote: >>>> It is at the end and contains exactly what is needed to synchronize. Not >>> The sync is simply single global synchronize_rcu(), and why bother to add >>> extra >=40bytes for each hctx. >>> >>>> sure what you mean by reuse hctx->srcu? >>> You already reuses hctx->srcu, but not see reason to add extra rcu_synchronize >>> to each hctx for just simulating one single synchronize_rcu(). >> >> To sync srcu together, the extra bytes must be needed, seperate blocking >> and non blocking queue to two hctx may be a not good choice. >> >> There is two choice: the struct rcu_synchronize is added in hctx or in srcu. >> Though add rcu_synchronize in srcu has a weakness: the extra bytes is >> not need if which do not need batch sync srcu, I still think it's better >> for the SRCU to provide the batch synchronization interface. > > The 'struct rcu_synchronize' can be allocated from heap or even stack( > if no too many NSs), which is just one shot sync and the API is supposed > to be called in slow path. No need to allocate it as long lifetime variable. > Especially 'struct srcu_struct' has already been too fat. Stack is not suitable, stack can not provide so many space for many name space. Heap maybe a choice, but need to add abnormal treat when alloc memory failed, Thus io pause time can not be ensured. So the extra space may must be needed for batch srcu sync. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme