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Fri, 31 Jul 2020 17:00:48 +0800 Received: from dggeme756-chm.china.huawei.com ([10.6.80.68]) by dggeme756-chm.china.huawei.com ([10.6.80.68]) with mapi id 15.01.1913.007; Fri, 31 Jul 2020 17:00:48 +0800 From: Zhanghailiang To: Lukas Straub , Derek Su Subject: RE: [PATCH v1 0/1] COLO: migrate dirty ram pages before colo checkpoint Thread-Topic: [PATCH v1 0/1] COLO: migrate dirty ram pages before colo checkpoint Thread-Index: AQHWR3EcmDhsnQsjxEWJOGaLUtyUkKkhCgeAgACOQaA= Date: Fri, 31 Jul 2020 09:00:48 +0000 Message-ID: References: <20200621021004.5559-1-dereksu@qnap.com> <20200731094940.7a26e583@luklap> In-Reply-To: <20200731094940.7a26e583@luklap> Accept-Language: zh-CN, en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.174.185.139] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.187; envelope-from=zhang.zhanghailiang@huawei.com; helo=huawei.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/31 05:00:49 X-ACL-Warn: Detected OS = Linux 3.11 and newer [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: , Cc: "chyang@qnap.com" , "quintela@redhat.com" , "qemu-devel@nongnu.org" , "dgilbert@redhat.com" , "ctcheng@qnap.com" , "jwsu1986@gmail.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Lukas Straub & Derek, Sorry for the late reply, too busy these days ;) > -----Original Message----- > From: Lukas Straub [mailto:lukasstraub2@web.de] > Sent: Friday, July 31, 2020 3:52 PM > To: Derek Su > Cc: qemu-devel@nongnu.org; Zhanghailiang > ; chyang@qnap.com; > quintela@redhat.com; dgilbert@redhat.com; ctcheng@qnap.com; > jwsu1986@gmail.com > Subject: Re: [PATCH v1 0/1] COLO: migrate dirty ram pages before colo > checkpoint >=20 > On Sun, 21 Jun 2020 10:10:03 +0800 > Derek Su wrote: >=20 > > This series is to reduce the guest's downtime during colo checkpoint > > by migrating dirty ram pages as many as possible before colo checkpoint= . > > > > If the iteration count reaches COLO_RAM_MIGRATE_ITERATION_MAX or > ram > > pending size is lower than 'x-colo-migrate-ram-threshold', stop the > > ram migration and do colo checkpoint. > > > > Test environment: > > The both primary VM and secondary VM has 1GiB ram and 10GbE NIC for > FT > > traffic. > > One fio buffer write job runs on the guest. > > The result shows the total primary VM downtime is decreased by ~40%. > > > > Please help to review it and suggestions are welcomed. > > Thanks. >=20 > Hello Derek, > Sorry for the late reply. > I think this is not a good idea, because it unnecessarily introduces a de= lay > between checkpoint request and the checkpoint itself and thus impairs > network bound workloads due to increased network latency. Workloads that > are independent from network don't cause many checkpoints anyway, so it > doesn't help there either. >=20 Agreed, though it seems to reduce VM's downtime while do checkpoint, but It doesn't help to reduce network latency, because the network packages whi= ch are Different between SVM and PVM caused this checkpoint request, it will be bl= ocked Until finishing checkpoint process. > Hailang did have a patch to migrate ram between checkpoints, which should > help all workloads, but it wasn't merged back then. I think you can pick = it up > again, rebase and address David's and Eric's comments: > https://lore.kernel.org/qemu-devel/20200217012049.22988-3-zhang.zhang > hailiang@huawei.com/T/#u > =20 The second one is not merged, which can help reduce the downtime. > Hailang, are you ok with that? >=20 Yes. @Derek, please feel free to pick it up if you would like to ;) Thanks, Hailiang > Regards, > Lukas Straub