* 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. 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