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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 28023C43331 for ; Tue, 24 Mar 2020 16:14:56 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 EFBE22073E for ; Tue, 24 Mar 2020 16:14:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EFBE22073E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jGmBd-0001xK-1L; Tue, 24 Mar 2020 16:13:53 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jGmBc-0001xE-9m for xen-devel@lists.xenproject.org; Tue, 24 Mar 2020 16:13:52 +0000 X-Inumbo-ID: 734495a0-6dea-11ea-8471-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 734495a0-6dea-11ea-8471-12813bfff9fa; Tue, 24 Mar 2020 16:13:51 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B6A07ACC2; Tue, 24 Mar 2020 16:13:50 +0000 (UTC) To: Hongyan Xia References: From: Jan Beulich Message-ID: <37dcd2d8-8ffe-a58e-4c7a-6dafc935b1c1@suse.com> Date: Tue, 24 Mar 2020 17:13:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Xen-devel] [PATCH] Revert "domctl: improve locking during domain destruction" X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Stefano Stabellini , Julien Grall , Wei Liu , Andrew Cooper , Ian Jackson , George Dunlap , xen-devel@lists.xenproject.org Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 24.03.2020 16:21, Hongyan Xia wrote: > From: Hongyan Xia > > Unfortunately, even though that commit dropped the domctl lock and > allowed other domctl to continue, it created severe lock contention > within domain destructions themselves. Multiple domain destructions in > parallel now spin for the global heap lock when freeing memory and could > spend a long time before the next hypercall continuation. I'm not at all happy to see this reverted; instead I was hoping that we could drop the domctl lock in further cases. If a lack of continuations is the problem, did you try forcing them to occur more frequently? > In contrast, > after dropping that commit, parallel domain destructions will just fail > to take the domctl lock, creating a hypercall continuation and backing > off immediately, allowing the thread that holds the lock to destroy a > domain much more quickly and allowing backed-off threads to process > events and irqs. > > On a 144-core server with 4TiB of memory, destroying 32 guests (each > with 4 vcpus and 122GiB memory) simultaneously takes: > > before the revert: 29 minutes > after the revert: 6 minutes This wants comparing against numbers demonstrating the bad effects of the global domctl lock. Iirc they were quite a bit higher than 6 min, perhaps depending on guest properties. Jan