From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v1 3/3] virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM Date: Mon, 9 Mar 2020 06:24:24 -0400 Message-ID: <20200309062311-mutt-send-email-mst@kernel.org> References: <20200205163402.42627-1-david@redhat.com> <20200205163402.42627-4-david@redhat.com> <20200216044641-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Tyler Sanderson Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, virtualization@lists.linux-foundation.org, Wei Wang , Alexander Duyck , David Rientjes , Nadav Amit , Michal Hocko List-Id: virtualization@lists.linuxfoundation.org On Sat, Mar 07, 2020 at 08:47:25PM -0800, Tyler Sanderson wrote: > Tested-by: Tyler Sanderson > > 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. OK this is now queued for -next. Tyler thanks a lot for the detailed test report - it's really awesome! I included it in the commit log in full so that if we need to come back to this it's easy to reproduce the testing. -- MST