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David Alan Gilbert" , Markus Armbruster References: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com> <20201126151734.743849-7-andrey.gruzdev@virtuozzo.com> <20201127222811.GJ6573@xz-x1> <20201130164037.GC3277@xz-x1> From: Andrey Gruzdev Message-ID: <2fb23634-9099-c25d-305d-b0568669e5c5@virtuozzo.com> Date: Mon, 30 Nov 2020 22:30:03 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 In-Reply-To: <20201130164037.GC3277@xz-x1> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [95.165.26.68] X-ClientProxiedBy: AM3PR07CA0121.eurprd07.prod.outlook.com (2603:10a6:207:7::31) To VI1PR0802MB2510.eurprd08.prod.outlook.com (2603:10a6:800:ad::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [192.168.1.64] (95.165.26.68) by AM3PR07CA0121.eurprd07.prod.outlook.com (2603:10a6:207:7::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3632.8 via Frontend Transport; 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envelope-from=andrey.gruzdev@virtuozzo.com; helo=EUR01-DB5-obe.outbound.protection.outlook.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 30.11.2020 19:40, Peter Xu wrote: > On Mon, Nov 30, 2020 at 11:11:00AM +0300, Andrey Gruzdev wrote: >> On 28.11.2020 01:28, Peter Xu wrote: >>> On Thu, Nov 26, 2020 at 06:17:34PM +0300, Andrey Gruzdev wrote: >>>> Since reading UFFD events and saving paged data are performed >>>> from the same thread, write fault latencies are sensitive to >>>> migration stream stalls. Limiting total page saving rate is a >>>> method to reduce amount of noticiable fault resolution latencies. >>>> >>>> Migration bandwidth limiting is achieved via noticing cases of >>>> out-of-threshold write fault latencies and temporarily disabling >>>> (strictly speaking, severely throttling) saving non-faulting pages. >>> >>> So have you done any measurements out of it, as we've talked in previous >>> version? Thanks, >>> >> >> Sorry, not done yet. > > So do you still plan to? :) > > And if not, could you describe the rational behind this patch? For example, > what's the problem behind (e.g., guest hangs for xxx seconds, maybe?) and > what's the outcome (guest doesn't hang any more)? > > Thanks, > Yes, I think providing a latency histogram with description of the test case is the right thing. -- Andrey Gruzdev, Principal Engineer Virtuozzo GmbH +7-903-247-6397 virtuzzo.com