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Tue, 16 Jun 2020 09:58:49 +0000 (UTC) Date: Tue, 16 Jun 2020 10:58:46 +0100 From: "Dr. David Alan Gilbert" To: zhukeqian Subject: Re: [PATCH v2] migration: Count new_dirty instead of real_dirty Message-ID: <20200616095846.GA2788@work-vm> References: <20200616021059.25984-1-zhukeqian1@huawei.com> <20200616093551.GA2790@work-vm> <3a45d5a0-3acf-336d-520f-523bf588b551@huawei.com> MIME-Version: 1.0 In-Reply-To: <3a45d5a0-3acf-336d-520f-523bf588b551@huawei.com> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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=205.139.110.61; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/16 02:01:17 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=_AUTOLEARN 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, Paolo Bonzini , Juan Quintela , Chao Fan , qemu-devel@nongnu.org, qemu-arm@nongnu.org, jianjay.zhou@huawei.com, wanghaibin.wang@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * zhukeqian (zhukeqian1@huawei.com) wrote: > Hi Dave, > > On 2020/6/16 17:35, Dr. David Alan Gilbert wrote: > > * Keqian Zhu (zhukeqian1@huawei.com) wrote: > >> real_dirty_pages becomes equal to total ram size after dirty log sync > >> in ram_init_bitmaps, the reason is that the bitmap of ramblock is > >> initialized to be all set, so old path counts them as "real dirty" at > >> beginning. > >> > >> This causes wrong dirty rate and false positive throttling at the end > >> of first ram save iteration. > >> > >> Signed-off-by: Keqian Zhu > > > > Since this function already returns num_dirty, why not just change the > > caller to increment a counter based off the return value? > Yes, that would be better :-) . > > > > > Can you point to the code which is using this value that triggers the > > throttle? > > > In migration_trigger_throttle(), rs->num_dirty_pages_period is used. > And it corresponds to real_dirty_pages here. OK; so is the problem not the same as the check that's in there for blk_mig_bulk_activate - don't we need to do the same trick for ram bulk migration (i.e. the first pass). Dave > Thanks, > Keqian > > > Dave > > > > > [...] > >> > >> > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > > > . > > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK