Re: [PATCH 0/6] migration/postcopy: enable compress during postcopy

[Wei Yang <richardw.yang@linux.intel.com>]

On Wed, Nov 06, 2019 at 08:11:44PM +0000, Dr. David Alan Gilbert wrote:
>* Wei Yang (richardw.yang@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)

>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 / dgilbert@redhat.com / Manchester, UK

-- 
Wei Yang
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