On Mon, Mar 09, 2020 at 10:03:14AM +0100, David Hildenbrand wrote: > On 08.03.20 05:47, Tyler Sanderson wrote: > > Tested-by: Tyler Sanderson <tysand@xxxxxxxxxx> > > > > Test setup: VM with 16 CPU, 64GB RAM. Running Debian 10. We have a 42 > > GB file full of random bytes that we continually cat to /dev/null. > > This fills the page cache as the file is read. Meanwhile we trigger > > the balloon to inflate, with a target size of 53 GB. This setup causes > > the balloon inflation to pressure the page cache as the page cache is > > also trying to grow. Afterwards we shrink the balloon back to zero (so > > total deflate = total inflate). > > > > Without patch (kernel 4.19.0-5): > > Inflation never reaches the target until we stop the "cat file > > > /dev/null" process. Total inflation time was 542 seconds. The longest > > period that made no net forward progress was 315 seconds (see attached > > graph). > > Result of "grep balloon /proc/vmstat" after the test: > > balloon_inflate 154828377 > > balloon_deflate 154828377 > > > > With patch (kernel 5.6.0-rc4+): > > Total inflation duration was 63 seconds. No deflate-queue activity > > occurs when pressuring the page-cache. > > Result of "grep balloon /proc/vmstat" after the test: > > balloon_inflate 12968539 > > balloon_deflate 12968539 > > > > Conclusion: This patch fixes the issue. In the test it reduced > > inflate/deflate activity by 12x, and reduced inflation time by 8.6x. > > But more importantly, if we hadn't killed the "grep balloon > > /proc/vmstat" process then, without the patch, the inflation process > > would never reach the target. > > > > Attached is a png of a graph showing the problematic behavior without > > this patch. It shows deflate-queue activity increasing linearly while > > balloon size stays constant over the course of more than 8 minutes of > > the test. > > Thanks a lot for the extended test! Given we shipped this for a long time, I think the best way to make progress is to merge 1/3, 2/3 right now, and 3/3 in the next release. > -- > Thanks, > > David / dhildenb _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
