From: "Li, Liang Z" <liang.z.li@intel.com> To: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: "rkagan@virtuozzo.com" <rkagan@virtuozzo.com>, "linux-kernel@vger.kenel.org" <linux-kernel@vger.kenel.org>, "ehabkost@redhat.com" <ehabkost@redhat.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "mst@redhat.com" <mst@redhat.com>, "simhan@hpe.com" <simhan@hpe.com>, "quintela@redhat.com" <quintela@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "jitendra.kolhe@hpe.com" <jitendra.kolhe@hpe.com>, "mohan_parthasarathy@hpe.com" <mohan_parthasarathy@hpe.com>, "amit.shah@redhat.com" <amit.shah@redhat.com>, "pbonzini@redhat.com" <pbonzini@redhat.com>, Wei Yang <richard.weiyang@huawei.com>, "rth@twiddle.net" <rth@twiddle.net> Subject: Re: [RFC Design Doc]Speed up live migration by skipping free pages Date: Thu, 24 Mar 2016 14:50:56 +0000 [thread overview] Message-ID: <F2CBF3009FA73547804AE4C663CAB28E0415BD6F@shsmsx102.ccr.corp.intel.com> (raw) In-Reply-To: <20160324102354.GB2230@work-vm> > > > > >> Given the typical speed of networks; it wouldn't do too much > > > > >> harm to start sending assuming all pages are dirty and then > > > > >> when the guest finally gets around to finishing the bitmap then > > > > >> update, so it's asynchronous - and then if the guest never > > > > >> responds we don't really > > > care. > > > > > > > > > >Indeed, thanks! > > > > > > > > > > > > > This is interesting. By doing so, the threshold I mentioned in > > > > another mail is not necessary, since we can do it in parallel. > > > > > > Actually I just realised it's a little more complex; we can't sync > > > the dirty bitmap again from the guest until after we've received the > guests 'free' > > > bitmap; that's because we wouldn't know if a 'dirty' page reflected > > > that a page declared as 'free' had now been reused - so there is > > > still an ordering there. > > > > > > Dave > > > > Not very complex, we can implement like this: > > > > 1. Set all the bits in the migration_bitmap_rcu->bmap to 1 2. Clear > > all the bits in ram_list. dirty_memory[DIRTY_MEMORY_MIGRATION] > > 3. Send the get_free_page_bitmap request 4. Start to send pages to > > destination and check if the free_page_bitmap is ready > > if (is_ready) { > > filter out the free pages from migration_bitmap_rcu->bmap; > > migration_bitmap_sync(); > > } > > continue until live migration complete. > > > > > > Is that right? > > The order I'm trying to understand is something like: > > a) Send the get_free_page_bitmap request > b) Start sending pages > c) Reach the end of memory > [ is_ready is false - guest hasn't made free map yet ] > d) normal migration_bitmap_sync() at end of first pass > e) Carry on sending dirty pages > f) is_ready is true > f.1) filter out free pages? > f.2) migration_bitmap_sync() > > It's f.1 I'm worried about. If the guest started generating the free bitmap > before (d), then a page marked as 'free' in f.1 might have become dirty > before (d) and so (f.2) doesn't set the dirty again, and so we can't filter out > pages in f.1. > As you described, the order is incorrect. Liang > Dave > > > > > Liang > > > > > > > > > > > >Liang > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
WARNING: multiple messages have this Message-ID (diff)
From: "Li, Liang Z" <liang.z.li@intel.com> To: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: "rkagan@virtuozzo.com" <rkagan@virtuozzo.com>, "linux-kernel@vger.kenel.org" <linux-kernel@vger.kenel.org>, "ehabkost@redhat.com" <ehabkost@redhat.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "mst@redhat.com" <mst@redhat.com>, "simhan@hpe.com" <simhan@hpe.com>, "quintela@redhat.com" <quintela@redhat.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "jitendra.kolhe@hpe.com" <jitendra.kolhe@hpe.com>, "mohan_parthasarathy@hpe.com" <mohan_parthasarathy@hpe.com>, "amit.shah@redhat.com" <amit.shah@redhat.com>, "pbonzini@redhat.com" <pbonzini@redhat.com>, Wei Yang <richard.weiyang@huawei.com>, "rth@twiddle.net" <rth@twiddle.net> Subject: Re: [Qemu-devel] [RFC Design Doc]Speed up live migration by skipping free pages Date: Thu, 24 Mar 2016 14:50:56 +0000 [thread overview] Message-ID: <F2CBF3009FA73547804AE4C663CAB28E0415BD6F@shsmsx102.ccr.corp.intel.com> (raw) In-Reply-To: <20160324102354.GB2230@work-vm> > > > > >> Given the typical speed of networks; it wouldn't do too much > > > > >> harm to start sending assuming all pages are dirty and then > > > > >> when the guest finally gets around to finishing the bitmap then > > > > >> update, so it's asynchronous - and then if the guest never > > > > >> responds we don't really > > > care. > > > > > > > > > >Indeed, thanks! > > > > > > > > > > > > > This is interesting. By doing so, the threshold I mentioned in > > > > another mail is not necessary, since we can do it in parallel. > > > > > > Actually I just realised it's a little more complex; we can't sync > > > the dirty bitmap again from the guest until after we've received the > guests 'free' > > > bitmap; that's because we wouldn't know if a 'dirty' page reflected > > > that a page declared as 'free' had now been reused - so there is > > > still an ordering there. > > > > > > Dave > > > > Not very complex, we can implement like this: > > > > 1. Set all the bits in the migration_bitmap_rcu->bmap to 1 2. Clear > > all the bits in ram_list. dirty_memory[DIRTY_MEMORY_MIGRATION] > > 3. Send the get_free_page_bitmap request 4. Start to send pages to > > destination and check if the free_page_bitmap is ready > > if (is_ready) { > > filter out the free pages from migration_bitmap_rcu->bmap; > > migration_bitmap_sync(); > > } > > continue until live migration complete. > > > > > > Is that right? > > The order I'm trying to understand is something like: > > a) Send the get_free_page_bitmap request > b) Start sending pages > c) Reach the end of memory > [ is_ready is false - guest hasn't made free map yet ] > d) normal migration_bitmap_sync() at end of first pass > e) Carry on sending dirty pages > f) is_ready is true > f.1) filter out free pages? > f.2) migration_bitmap_sync() > > It's f.1 I'm worried about. If the guest started generating the free bitmap > before (d), then a page marked as 'free' in f.1 might have become dirty > before (d) and so (f.2) doesn't set the dirty again, and so we can't filter out > pages in f.1. > As you described, the order is incorrect. Liang > Dave > > > > > Liang > > > > > > > > > > > >Liang > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2016-03-24 14:50 UTC|newest] Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-03-22 7:43 [RFC Design Doc]Speed up live migration by skipping free pages Liang Li 2016-03-22 7:43 ` [Qemu-devel] " Liang Li 2016-03-22 10:11 ` Michael S. Tsirkin 2016-03-22 10:11 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-23 6:05 ` Li, Liang Z 2016-03-23 6:05 ` [Qemu-devel] " Li, Liang Z 2016-03-23 14:08 ` Michael S. Tsirkin 2016-03-23 14:08 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 1:19 ` Li, Liang Z 2016-03-24 1:19 ` [Qemu-devel] " Li, Liang Z 2016-03-24 9:48 ` Michael S. Tsirkin 2016-03-24 9:48 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 10:16 ` Li, Liang Z 2016-03-24 10:16 ` [Qemu-devel] " Li, Liang Z 2016-03-24 10:29 ` Michael S. Tsirkin 2016-03-24 10:29 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 14:33 ` Li, Liang Z 2016-03-24 14:33 ` [Qemu-devel] " Li, Liang Z 2016-03-24 14:44 ` Michael S. Tsirkin 2016-03-24 14:44 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 15:16 ` Li, Liang Z 2016-03-24 15:16 ` [Qemu-devel] " Li, Liang Z 2016-03-24 15:18 ` Paolo Bonzini 2016-03-24 15:18 ` [Qemu-devel] " Paolo Bonzini 2016-03-24 15:25 ` Li, Liang Z 2016-03-24 15:25 ` [Qemu-devel] " Li, Liang Z 2016-03-24 15:27 ` Michael S. Tsirkin 2016-03-24 15:27 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 15:39 ` Li, Liang Z 2016-03-24 15:39 ` [Qemu-devel] " Li, Liang Z 2016-03-24 15:47 ` Paolo Bonzini 2016-03-24 15:47 ` [Qemu-devel] " Paolo Bonzini 2016-03-24 15:59 ` Li, Liang Z 2016-03-24 15:59 ` [Qemu-devel] " Li, Liang Z 2016-03-22 19:05 ` Dr. David Alan Gilbert 2016-03-22 19:05 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-03-23 6:48 ` Li, Liang Z 2016-03-23 6:48 ` [Qemu-devel] " Li, Liang Z 2016-03-24 1:24 ` Wei Yang 2016-03-24 1:24 ` [Qemu-devel] " Wei Yang 2016-03-24 9:00 ` Dr. David Alan Gilbert 2016-03-24 9:00 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-03-24 10:09 ` Li, Liang Z 2016-03-24 10:09 ` [Qemu-devel] " Li, Liang Z 2016-03-24 10:23 ` Dr. David Alan Gilbert 2016-03-24 10:23 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-03-24 14:50 ` Li, Liang Z [this message] 2016-03-24 14:50 ` Li, Liang Z 2016-03-24 15:11 ` Michael S. Tsirkin 2016-03-24 15:11 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 15:53 ` Li, Liang Z 2016-03-24 15:53 ` [Qemu-devel] " Li, Liang Z 2016-03-24 15:56 ` Michael S. Tsirkin 2016-03-24 15:56 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 16:05 ` Li, Liang Z 2016-03-24 16:05 ` [Qemu-devel] " Li, Liang Z 2016-03-24 16:25 ` Michael S. Tsirkin 2016-03-24 16:25 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-24 17:49 ` Dr. David Alan Gilbert 2016-03-24 17:49 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-03-24 22:16 ` Michael S. Tsirkin 2016-03-24 22:16 ` [Qemu-devel] " Michael S. Tsirkin 2016-03-25 1:59 ` Li, Liang Z 2016-03-25 1:59 ` [Qemu-devel] " Li, Liang Z 2016-03-25 1:32 ` Li, Liang Z 2016-03-25 1:32 ` [Qemu-devel] " Li, Liang Z 2016-04-18 11:08 ` Li, Liang Z 2016-04-18 11:08 ` [Qemu-devel] " Li, Liang Z 2016-04-18 11:29 ` Michael S. Tsirkin 2016-04-18 11:29 ` [Qemu-devel] " Michael S. Tsirkin 2016-04-18 14:36 ` Li, Liang Z 2016-04-18 14:36 ` [Qemu-devel] " Li, Liang Z 2016-04-18 15:38 ` Michael S. Tsirkin 2016-04-18 15:38 ` [Qemu-devel] " Michael S. Tsirkin 2016-04-19 2:20 ` Li, Liang Z 2016-04-19 2:20 ` [Qemu-devel] " Li, Liang Z 2016-04-19 19:12 ` Dr. David Alan Gilbert 2016-04-19 19:12 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-04-25 10:56 ` Michael S. Tsirkin 2016-04-25 10:56 ` [Qemu-devel] " Michael S. Tsirkin 2016-04-19 19:05 ` Dr. David Alan Gilbert 2016-04-19 19:05 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-04-20 3:22 ` Li, Liang Z 2016-04-20 3:22 ` [Qemu-devel] " Li, Liang Z 2016-04-20 8:10 ` Dr. David Alan Gilbert 2016-04-20 8:10 ` [Qemu-devel] " Dr. David Alan Gilbert 2016-03-25 1:32 ` Li, Liang Z 2016-03-25 1:32 ` [Qemu-devel] " Li, Liang Z 2016-04-01 10:54 ` Amit Shah 2016-04-01 10:54 ` [Qemu-devel] " Amit Shah 2016-04-05 1:49 ` Li, Liang Z 2016-04-05 1:49 ` [Qemu-devel] " Li, Liang Z 2016-03-23 1:37 ` Wei Yang 2016-03-23 1:37 ` [Qemu-devel] " Wei Yang 2016-03-23 7:18 ` Li, Liang Z 2016-03-23 7:18 ` [Qemu-devel] " Li, Liang Z 2016-03-23 9:46 ` Wei Yang 2016-03-23 9:46 ` [Qemu-devel] " Wei Yang 2016-03-23 14:35 ` Li, Liang Z 2016-03-23 14:35 ` [Qemu-devel] " Li, Liang Z 2016-03-24 0:52 ` Wei Yang 2016-03-24 0:52 ` [Qemu-devel] " Wei Yang 2016-03-24 1:32 ` Li, Liang Z 2016-03-24 1:32 ` [Qemu-devel] " Li, Liang Z 2016-03-24 1:56 ` Wei Yang 2016-03-24 1:56 ` [Qemu-devel] " Wei Yang 2016-03-23 16:53 ` Eric Blake 2016-03-23 16:53 ` Eric Blake 2016-03-23 21:41 ` Wei Yang 2016-03-23 21:41 ` Wei Yang 2016-03-24 1:23 ` Li, Liang Z 2016-03-24 1:23 ` Li, Liang Z
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