On Wed, Apr 25, 2018 at 01:27:02PM +0200, Juan Quintela wrote: > > Hi > > > [v12] > > Big news, it is not RFC anymore, it works reliabely for me. > > Changes: > - Locknig changed completely (several times) > - We now send all pages through the channels. In a 2GB guest with 1 disk > and a network card, the amount of data send for RAM was 80KB. > - This is not optimized yet, but it shouws clear improvements over precopy. > testing over localhost networking I can guet: > - 2 VCPUs guest > - 2GB RAM > - runn stress --vm 4 --vm 500GB (i.e. dirtying 2GB or RAM each second) > > - Total time: precopy ~50seconds, multifd around 11seconds > - Bandwidth usage is around 273MB/s vs 71MB/s on the same hardware > > This is very preleminary testing, will send more numbers when I got them. > But looks promissing. > > Things that will be improved later: > - Initial synchronization is too slow (around 1s) > - We synchronize all threads after each RAM section, we can move to only > synchronize them after we have done a bitmap syncrhronization > - We can improve bitmap walking (but that is independent of multifd)
Hi, Juan, I got some high level review comments and notes: - This series may need to rebase after Guangrong's cleanup series. - Looks like now we allow multifd and compression be enabled together. Shall we restrict on that? - Is multifd only for TCP? If so, do we check against that? E.g., should we fail the unix/fd/exec migrations when multifd is enabled? - Why init sync is slow (1s)? Is there any clue of that problem? - Currently the sync between threads are still very complicated to me... we have these on the sender side (I didn't dig the recv side): - two global semaphores in multifd_send_state, - one mutex and two semaphores in each of the send thread, So in total we'll have 2+3*N such locks/sems. I'm thinking whether we can further simplify the sync logic a bit... Thanks, -- Peter Xu
