Re: [PATCH v3] migration: clear the memory region dirty bitmap when skipping free pages

[David Hildenbrand]

On 22.07.21 19:41, Peter Xu wrote:
> On Thu, Jul 22, 2021 at 04:51:48PM +0200, David Hildenbrand wrote:
> > I'll give it a churn.
>
> Thanks, David.

Migration of a 8 GiB VM
* within the same host
* after Linux is up and idle
* free page hinting enabled
* after dirtying most VM memory using memhog
* keeping bandwidth set to QEMU defaults
* On my 16 GiB notebook with other stuff running


Current upstream with 63268c4970a, without this patch:

total time: 28606 ms
downtime: 33 ms
setup: 3 ms
transferred ram: 3722913 kbytes
throughput: 1066.37 mbps
remaining ram: 0 kbytes
total ram: 8389384 kbytes
duplicate: 21674 pages
skipped: 0 pages
normal: 928866 pages
normal bytes: 3715464 kbytes
dirty sync count: 5
pages-per-second: 32710

Current upstream without 63268c4970a, without this patch:

total time: 28530 ms
downtime: 277 ms
setup: 4 ms
transferred ram: 3726266 kbytes
throughput: 1070.21 mbps
remaining ram: 0 kbytes
total ram: 8389384 kbytes
duplicate: 21890 pages
skipped: 0 pages
normal: 929702 pages
normal bytes: 3718808 kbytes
dirty sync count: 5
pages-per-second: 32710


Current upstream without 63268c4970a, with this patch:

total time: 5115 ms
downtime: 37 ms
setup: 5 ms
transferred ram: 659532 kbytes
throughput: 1057.94 mbps
remaining ram: 0 kbytes
total ram: 8389384 kbytes
duplicate: 20748 pages
skipped: 0 pages
normal: 164516 pages
normal bytes: 658064 kbytes
dirty sync count: 4
pages-per-second: 32710


Current upstream with 63268c4970a, with this patch:

total time: 5205 ms
downtime: 45 ms
setup: 3 ms
transferred ram: 659636 kbytes
throughput: 1039.39 mbps
remaining ram: 0 kbytes
total ram: 8389384 kbytes
duplicate: 20264 pages
skipped: 0 pages
normal: 164543 pages
normal bytes: 658172 kbytes
dirty sync count: 4
pages-per-second: 32710



I repeated the last two measurements two times and took the "better" 
results.

Looks like this patch does it job and that 63268c4970a doesn't seem to 
degrade migration in this combination/setup significantly (if at all, we 
would have to do more measurements).

--
Thanks,

David / dhildenb