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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 9632EC433F5 for ; Tue, 5 Apr 2022 15:06:54 +0000 (UTC) Received: from localhost ([::1]:53172 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nbklh-0003zl-LE for qemu-devel@archiver.kernel.org; Tue, 05 Apr 2022 11:06:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45118) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nbkjZ-0002eE-8g for qemu-devel@nongnu.org; Tue, 05 Apr 2022 11:04:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51908) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nbkjW-0000Gt-RV for qemu-devel@nongnu.org; Tue, 05 Apr 2022 11:04:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649171077; 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=jNg/8uxrXw+ea7GVVLrVExsSzlGwbJrbJPijvI6Vvkc=; b=Mr3p6r0QorJbUYqb0IeOCy4SURU/bzudefJHe4aVb/ZS58GozANot383an70RaqUjRZFLM fMt7yJWJJxS1yi0U5TvI0zxjk0p1GkgIh74aS8cuCkRgnZgi+6TXj2P+JGpmO35VRjw2Mc LYqp0umGE5An+6xEK6geioAhyUFBxfw= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-266-hCDG5pW3O2Ohn59NCrdDUQ-1; Tue, 05 Apr 2022 11:04:36 -0400 X-MC-Unique: hCDG5pW3O2Ohn59NCrdDUQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 151B6899EC1; Tue, 5 Apr 2022 15:04:36 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.82]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9D81D1415129; Tue, 5 Apr 2022 15:04:34 +0000 (UTC) Date: Tue, 5 Apr 2022 17:04:32 +0200 From: Kevin Wolf To: Emanuele Giuseppe Esposito Subject: Re: [PATCH] block/stream: Drain subtree around graph change Message-ID: References: <20220324125756.9950-1-hreitz@redhat.com> <87fb6a17-c1e8-cb50-5f0f-3979b8cc5ca6@redhat.com> MIME-Version: 1.0 In-Reply-To: <87fb6a17-c1e8-cb50-5f0f-3979b8cc5ca6@redhat.com> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Hanna Reitz , Vladimir Sementsov-Ogievskiy , John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 05.04.2022 um 15:09 hat Emanuele Giuseppe Esposito geschrieben: > Am 05/04/2022 um 12:14 schrieb Kevin Wolf: > > I think all of this is really relevant for Emanuele's work, which > > involves adding AIO_WAIT_WHILE() deep inside graph update functions. I > > fully expect that we would see very similar problems, and just stacking > > drain sections over drain sections that might happen to usually fix > > things, but aren't guaranteed to, doesn't look like a good solution. > > Yes, I think at this point we all agreed to drop subtree_drain as > replacement for AioContext. > > The alternative is what Paolo proposed in the other thread " Removal of > AioContext lock, bs->parents and ->children: proof of concept" > I am not sure which thread you replied first :) This one, I think. :-) > I think that proposal is not far from your idea, and it avoids to > introduce or even use drains at all. > Not sure why you called it a "step backwards even from AioContext locks". I was only referring to the lock locality there. AioContext locks are really coarse, but still a finer granularity than a single global lock. In the big picture, it's still be better than the AioContext lock, but that's because it's a different type of lock, not because it has better locality. So I was just wondering if we can't have the different type of lock and make it local to the BDS, too. Kevin