From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> To: "Li, Liang Z" <liang.z.li@intel.com> Cc: Wei Yang <richard.weiyang@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "linux-kernel@vger.kenel.org" <linux-kernel@vger.kenel.org>, "pbonzini@redhat.com" <pbonzini@redhat.com>, "rth@twiddle.net" <rth@twiddle.net>, "ehabkost@redhat.com" <ehabkost@redhat.com>, "mst@redhat.com" <mst@redhat.com>, "amit.shah@redhat.com" <amit.shah@redhat.com>, "quintela@redhat.com" <quintela@redhat.com>, "mohan_parthasarathy@hpe.com" <mohan_parthasarathy@hpe.com>, "jitendra.kolhe@hpe.com" <jitendra.kolhe@hpe.com>, "simhan@hpe.com" <simhan@hpe.com>, "rkagan@virtuozzo.com" <rkagan@virtuozzo.com>, "riel@redhat.com" <riel@redhat.com> Subject: Re: [RFC Design Doc]Speed up live migration by skipping free pages Date: Thu, 24 Mar 2016 10:23:55 +0000 [thread overview] Message-ID: <20160324102354.GB2230@work-vm> (raw) In-Reply-To: <F2CBF3009FA73547804AE4C663CAB28E0415B8E5@shsmsx102.ccr.corp.intel.com> * Li, Liang Z (liang.z.li@intel.com) wrote: > > * Wei Yang (richard.weiyang@huawei.com) wrote: > > > On Wed, Mar 23, 2016 at 06:48:22AM +0000, Li, Liang Z wrote: > > > [...] > > > >> > 8. Pseudo code > > > >> > Dirty page logging should be enabled before getting the free page > > > >> > information from guest, this is important because during the > > > >> > process of getting free pages, some free pages may be used and > > > >> > written by the guest, dirty page logging can trace these pages. > > > >> > The pseudo code is like below: > > > >> > > > > >> > ----------------------------------------------- > > > >> > MigrationState *s = migrate_get_current(); > > > >> > ... > > > >> > > > > >> > memory_global_dirty_log_start(); > > > >> > > > > >> > if (get_guest_mem_info(&info)) { > > > >> > while (!get_free_page_bmap(free_page_bitmap, > > > >> > drop_page_cache) > > > >> && > > > >> > s->state != MIGRATION_STATUS_CANCELLING) { > > > >> > usleep(1000) // sleep for 1 ms > > > >> > } > > > >> > > > > >> > tighten_free_page_bmap = > > > >> tighten_guest_free_pages(free_page_bitmap); > > > >> > filter_out_guest_free_pages(tighten_free_page_bmap); > > > >> > } > > > >> > > > >> 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. Dave > > Liang > > > > > > > > >Liang -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
WARNING: multiple messages have this Message-ID (diff)
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> To: "Li, Liang Z" <liang.z.li@intel.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 10:23:55 +0000 [thread overview] Message-ID: <20160324102354.GB2230@work-vm> (raw) In-Reply-To: <F2CBF3009FA73547804AE4C663CAB28E0415B8E5@shsmsx102.ccr.corp.intel.com> * Li, Liang Z (liang.z.li@intel.com) wrote: > > * Wei Yang (richard.weiyang@huawei.com) wrote: > > > On Wed, Mar 23, 2016 at 06:48:22AM +0000, Li, Liang Z wrote: > > > [...] > > > >> > 8. Pseudo code > > > >> > Dirty page logging should be enabled before getting the free page > > > >> > information from guest, this is important because during the > > > >> > process of getting free pages, some free pages may be used and > > > >> > written by the guest, dirty page logging can trace these pages. > > > >> > The pseudo code is like below: > > > >> > > > > >> > ----------------------------------------------- > > > >> > MigrationState *s = migrate_get_current(); > > > >> > ... > > > >> > > > > >> > memory_global_dirty_log_start(); > > > >> > > > > >> > if (get_guest_mem_info(&info)) { > > > >> > while (!get_free_page_bmap(free_page_bitmap, > > > >> > drop_page_cache) > > > >> && > > > >> > s->state != MIGRATION_STATUS_CANCELLING) { > > > >> > usleep(1000) // sleep for 1 ms > > > >> > } > > > >> > > > > >> > tighten_free_page_bmap = > > > >> tighten_guest_free_pages(free_page_bitmap); > > > >> > filter_out_guest_free_pages(tighten_free_page_bmap); > > > >> > } > > > >> > > > >> 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. Dave > > Liang > > > > > > > > >Liang -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
next prev parent reply other threads:[~2016-03-24 10:24 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 [this message] 2016-03-24 10:23 ` Dr. David Alan Gilbert 2016-03-24 14:50 ` Li, Liang Z 2016-03-24 14:50 ` [Qemu-devel] " 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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