On Fri, Mar 16, 2018 at 04:05:14PM +0800, Xiao Guangrong wrote: > > Hi David, > > Thanks for your review. > > On 03/15/2018 06:25 PM, Dr. David Alan Gilbert wrote: > > > > migration/ram.c | 32 ++++++++++++++++---------------- > > > > Hi, > > Do you have some performance numbers to show this helps? Were those > > taken on a normal system or were they taken with one of the compression > > accelerators (which I think the compression migration was designed for)? > > Yes, i have tested it on my desktop, i7-4790 + 16G, by locally live migrate > the VM which has 8 vCPUs + 6G memory and the max-bandwidth is limited to 350. > > During the migration, a workload which has 8 threads repeatedly written total > 6G memory in the VM. Before this patchset, its bandwidth is ~25 mbps, after > applying, the bandwidth is ~50 mbps. Hi, Guangrong, Not really review comments, but I got some questions. :) IIUC this patch will only change the behavior when last_sent_block changed. I see that the performance is doubled after the change, which is really promising. However I don't fully understand why it brings such a big difference considering that IMHO current code is sending dirty pages per-RAMBlock. I mean, IMHO last_sent_block should not change frequently? Or am I wrong? Another follow-up question would be: have you measured how long time needed to compress a 4k page, and how many time to send it? I think "sending the page" is not really meaningful considering that we just put a page into the buffer (which should be extremely fast since we don't really flush it every time), however I would be curious on how slow would compressing a page be. Thanks, > > BTW, Compression will use almost all valid bandwidth after all of our work > which i will post it out part by part. > -- Peter Xu
