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Thu, 6 Aug 2020 16:58:13 +0000 (UTC) Date: Thu, 6 Aug 2020 17:58:11 +0100 From: "Dr. David Alan Gilbert" To: Zheng Chuan Subject: Re: [RFC PATCH 0/8] *** A Method for evaluating dirty page rate *** Message-ID: <20200806165811.GI2711@work-vm> References: <1595646669-109310-1-git-send-email-zhengchuan@huawei.com> <20200804161902.GC2659@work-vm> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@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=207.211.31.81; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/06 05:03:13 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=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: zhang.zhanghailiang@huawei.com, quintela@redhat.com, linyilu@huawei.com, qemu-devel@nongnu.org, alex.chen@huawei.com, ann.zhuangyanying@huawei.com, fangying1@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Zheng Chuan (zhengchuan@huawei.com) wrote: > > > On 2020/8/5 0:19, Dr. David Alan Gilbert wrote: > > * Chuan Zheng (zhengchuan@huawei.com) wrote: > >> From: Zheng Chuan > > > > Hi, > > > >> Sometimes it is neccessary to evaluate dirty page rate before migration. > >> Users could decide whether to proceed migration based on the evaluation > >> in case of vm performance loss due to heavy workload. > >> Unlikey simulating dirtylog sync which could do harm on runnning vm, > >> we provide a sample-hash method to compare hash results for samping page. > >> In this way, it would have hardly no impact on vm performance. > >> > >> We evaluate the dirtypage rate on running vm. > >> The VM specifications for migration are as follows: > >> - VM use 4-K page; > >> - the number of VCPU is 32; > >> - the total memory is 32Gigabit; > >> - use 'mempress' tool to pressurize VM(mempress 4096 1024); > >> > >> ++++++++++++++++++++++++++++++++++++++++++ > >> | | dirtyrate | > >> ++++++++++++++++++++++++++++++++++++++++++ > >> | no mempress | 4MB/s | > >> ------------------------------------------ > >> | mempress 4096 1024 | 1204MB/s | > >> ++++++++++++++++++++++++++++++++++++++++++ > >> | mempress 4096 4096 | 4000Mb/s | > >> ++++++++++++++++++++++++++++++++++++++++++ > > > > This is quite neat; I know we've got other people who have asked > > for a similar feature! > > Have you tried to validate these numbers against a real migration - e.g. > > try setting mempress to dirty just under 1GByte/s and see if you can > > migrate it over a 10Gbps link? > > > > Dave > > > Hi, Dave. > Thank you for your review. > > Note that, the original intention is evaluating dirty rate before migration. Right, but the reason you want to evaluate the dirty rate is, I guess, to figure out whether a migration is likely to coverge? > However, I test dirty rate against a real migration over a bandwidth of 10Gps with various mempress, which shows as below: > ++++++++++++++++++++++++++++++++++++++++++ > | | dirtyrate | > ++++++++++++++++++++++++++++++++++++++++++ > | no mempress | 8MB/s | > ------------------------------------------ > | mempress 4096 1024 | 1188MB/s | > ++++++++++++++++++++++++++++++++++++++++++ > > It looks still close to actual dirty rate:) I don't quite understand that comparison you just gave. But what I was expecting was that a mempress that just fits teh ~1100MB/s is just the limit of what you can get down a 10Gbps link. Dave > Test results against a real migration will be posted in V2. > > >> Test dirtyrate by qmp command like this: > >> 1. virsh qemu-monitor-command [vmname] '{"execute":"cal_dirty_rate", "arguments": {"value": [sampletime]}}' > >> 2. virsh qemu-monitor-command [vmname] '{"execute":"get_dirty_rate"}' > >> > >> Further test dirtyrate by libvirt api like this: > >> virsh getdirtyrate [vmname] [sampletime] > >> > >> Zheng Chuan (8): > >> migration/dirtyrate: Add get_dirtyrate_thread() function > >> migration/dirtyrate: Add block_dirty_info to store dirtypage info > >> migration/dirtyrate: Add dirtyrate statistics series functions > >> migration/dirtyrate: Record hash results for each ramblock > >> migration/dirtyrate: Compare hash results for recorded ramblock > >> migration/dirtyrate: Implement get_sample_gap_period() and > >> block_sample_gap_period() > >> migration/dirtyrate: Implement calculate_dirtyrate() function > >> migration/dirtyrate: Implement > >> qmp_cal_dirty_rate()/qmp_get_dirty_rate() function > >> > >> migration/Makefile.objs | 1 + > >> migration/dirtyrate.c | 424 ++++++++++++++++++++++++++++++++++++++++++++++++ > >> migration/dirtyrate.h | 67 ++++++++ > >> qapi/migration.json | 24 +++ > >> qapi/pragma.json | 3 +- > >> 5 files changed, 518 insertions(+), 1 deletion(-) > >> create mode 100644 migration/dirtyrate.c > >> create mode 100644 migration/dirtyrate.h > >> > >> -- > >> 1.8.3.1 > >> > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > > > > > . > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK