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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCFEEC433FE for ; Tue, 23 Nov 2021 00:14:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231206AbhKWARJ (ORCPT ); Mon, 22 Nov 2021 19:17:09 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42546 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230394AbhKWARJ (ORCPT ); Mon, 22 Nov 2021 19:17:09 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1637626441; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JZvtms7pIknR/E/OjT1THTSkCWU334H5w7OLjmBgWow=; b=OoxLjCKnJ0ConmKTL+NKAVEExEBKQy1J0gzuHIT/Cxs0iaNoKNPobtivxB1vjCkzbZZq5+ tBg54wlV8mvbpba2k9Y/XmFqMOCxyJjv9ZZ6HWip2fyjopFz7I+pX4KDuoteF4/kiOnPLm VlQshf5qI80pwaDVHQ33T4KRguc+++c= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-380-c8SRk3RGPVGc_5sOf5nBDQ-1; Mon, 22 Nov 2021 19:13:58 -0500 X-MC-Unique: c8SRk3RGPVGc_5sOf5nBDQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 018E21018720; Tue, 23 Nov 2021 00:13:57 +0000 (UTC) Received: from T590 (ovpn-8-21.pek2.redhat.com [10.72.8.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2411D18428; Tue, 23 Nov 2021 00:13:45 +0000 (UTC) Date: Tue, 23 Nov 2021 08:13:41 +0800 From: Ming Lei To: Sagi Grimberg Cc: Christoph Hellwig , Jens Axboe , "Martin K . Petersen" , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, Keith Busch , Chao Leng Subject: Re: [PATCH 4/5] nvme: quiesce namespace queue in parallel Message-ID: References: <20211119021849.2259254-1-ming.lei@redhat.com> <20211119021849.2259254-5-ming.lei@redhat.com> <37036ab3-da87-898e-5af6-1abf228b4390@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <37036ab3-da87-898e-5af6-1abf228b4390@grimberg.me> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Mon, Nov 22, 2021 at 10:07:24AM +0200, Sagi Grimberg wrote: > > > On 11/19/21 4:18 AM, Ming Lei wrote: > > Chao Leng reported that in case of lots of namespaces, it may take quite a > > while for nvme_stop_queues() to quiesce all namespace queues. > > > > Improve nvme_stop_queues() by running quiesce in parallel, and just wait > > once if global quiesce wait is allowed. > > > > Link: https://lore.kernel.org/linux-block/cc732195-c053-9ce4-e1a7-e7f6dcf762ac@huawei.com/ > > Reported-by: Chao Leng > > Signed-off-by: Ming Lei > > --- > > drivers/nvme/host/core.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 4b5de8f5435a..06741d3ed72b 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -4517,9 +4517,7 @@ static void nvme_start_ns_queue(struct nvme_ns *ns) > > static void nvme_stop_ns_queue(struct nvme_ns *ns) > > { > > if (!test_and_set_bit(NVME_NS_STOPPED, &ns->flags)) > > - blk_mq_quiesce_queue(ns->queue); > > - else > > - blk_mq_wait_quiesce_done(ns->queue); > > + blk_mq_quiesce_queue_nowait(ns->queue); > > } > > /* > > @@ -4620,6 +4618,11 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl) > > down_read(&ctrl->namespaces_rwsem); > > list_for_each_entry(ns, &ctrl->namespaces, list) > > nvme_stop_ns_queue(ns); > > + list_for_each_entry(ns, &ctrl->namespaces, list) { > > + blk_mq_wait_quiesce_done(ns->queue); > > + if (blk_mq_global_quiesce_wait(ns->queue)) > > + break; > > + } > > up_read(&ctrl->namespaces_rwsem); > > > Can you quantify how much of a difference it is to do rcu_read_unlock() > for every queue? The big improvement here is that it is done in parallel > instead of serially. Just wandering if it is worth the less than elegant > interface... The biggest improvement is N * synchronize_rcu() -> 1 * synchronize_rcu() in case of non blocking, that is what Chao Leng complained before. Even for blocking case, the parallel quiesce is still good, such as, when one synchronize_srcu() is done, other srcu syncs should be done usually too. thanks, Ming