On Mon, Jun 03, 2019 at 10:35:27AM +0800, Peter Xu wrote: >On Mon, Jun 03, 2019 at 09:33:05AM +0800, Wei Yang wrote: >> On Sat, Jun 01, 2019 at 11:34:41AM +0800, Peter Xu wrote: >> >On Fri, May 31, 2019 at 05:43:37PM +0100, Dr. David Alan Gilbert wrote: >> >> * Wei Yang (richardw.y...@linux.intel.com) wrote: >> >> > During migration, we would sync bitmap from ram_list.dirty_memory to >> >> > RAMBlock.bmap in cpu_physical_memory_sync_dirty_bitmap(). >> >> > >> >> > Since we set RAMBlock.bmap and ram_list.dirty_memory both to all 1, this >> >> > means at the first round this sync is meaningless and is a duplicated >> >> > work. >> >> > >> >> > Leaving RAMBlock->bmap blank on allocating would have a side effect on >> >> > migration_dirty_pages, since it is calculated from the result of >> >> > cpu_physical_memory_sync_dirty_bitmap(). To keep it right, we need to >> >> > set migration_dirty_pages to 0 in ram_state_init(). >> >> > >> >> > Signed-off-by: Wei Yang <richardw.y...@linux.intel.com> >> >> >> >> I've looked at this for a while, and I think it's OK, so >> >> >> >> Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com> >> >> >> >> Peter, Juan: Can you just see if there's arny reason this would be bad, >> >> but I think it's actually more sensible than what we have. >> > >> >I really suspect it will work in all cases... Wei, have you done any >> >test (or better, thorough tests) with this change? My reasoning of >> >why we should need the bitmap all set is here: >> > >> >> I have done some migration cases, like migrate a linux guest through tcp. > >When did you start the migration? Have you tried to migrate during >some workload? >
I tried kernel build in guest. >> >> Other cases suggested to do? > >Could you also help answer the question I raised below in the link? > >Thanks, > >> >https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg07361.html > I took a look into this link, hope my understanding is correct. You concern is this thread/patch is based on one prerequisite -- dirty all the bitmap at start. My answer is we already did it in ram_block_add() for each RAMBlock. And then the bitmap is synced by migration_bitmap_sync_precopy() from ram_list.dirty_memory to RAMBlock.bmap. >-- >Peter Xu -- Wei Yang Help you, Help me
