On Thu, Nov 07, 2019 at 09:15:44AM +0000, Dr. David Alan Gilbert wrote: >* Wei Yang (richardw.y...@linux.intel.com) wrote: >> On Wed, Nov 06, 2019 at 08:11:44PM +0000, Dr. David Alan Gilbert wrote: >> >* Wei Yang (richardw.y...@linux.intel.com) wrote: >> >> This patch set tries enable compress during postcopy. >> >> >> >> postcopy requires to place a whole host page, while migration thread >> >> migrate >> >> memory in target page size. This makes postcopy need to collect all target >> >> pages in one host page before placing via userfaultfd. >> >> >> >> To enable compress during postcopy, there are two problems to solve: >> >> >> >> 1. Random order for target page arrival >> >> 2. Target pages in one host page arrives without interrupt by target >> >> page from other host page >> >> >> >> The first one is handled by counting the number of target pages arrived >> >> instead of the last target page arrived. >> >> >> >> The second one is handled by: >> >> >> >> 1. Flush compress thread for each host page >> >> 2. Wait for decompress thread for before placing host page >> >> >> >> With the combination of these two changes, compress is enabled during >> >> postcopy. >> > >> >What have you tested this with? 2MB huge pages I guess? >> > >> >> I tried with this qemu option: >> >> -object >> memory-backend-file,id=mem1,mem-path=/dev/hugepages/guest2,size=4G \ >> -device pc-dimm,id=dimm1,memdev=mem1 >> >> /dev/hugepages/guest2 is a file under hugetlbfs >> >> hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M) > >OK, yes that should be fine. >I suspect on Power/ARM where they have normal memory with 16/64k pages, >the cost of the flush will mean compression is more expensive in >postcopy mode; but still makes it possible. >
Not get your point clearly about more expensive. You mean more expensive on ARM/Power? If the solution looks good to you, I would prepare v2. >Dave > >> >Dave >> > >> >> Wei Yang (6): >> >> migration/postcopy: reduce memset when it is zero page and >> >> matches_target_page_size >> >> migration/postcopy: wait for decompress thread in precopy >> >> migration/postcopy: count target page number to decide the >> >> place_needed >> >> migration/postcopy: set all_zero to true on the first target page >> >> migration/postcopy: enable random order target page arrival >> >> migration/postcopy: enable compress during postcopy >> >> >> >> migration/migration.c | 11 -------- >> >> migration/ram.c | 65 ++++++++++++++++++++++++++++++------------- >> >> 2 files changed, 45 insertions(+), 31 deletions(-) >> >> >> >> -- >> >> 2.17.1 >> >> >> >-- >> >Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK >> >> -- >> Wei Yang >> Help you, Help me >-- >Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK -- Wei Yang Help you, Help me