On 7/2/18 3:26 PM, Andrew Morton wrote: > On Fri, 29 Jun 2018 15:25:28 -0400 Josef Bacik <josef@xxxxxxxxxxxxxx> wrote: > >> This series adds a latency based io controller for cgroups. It is based on the >> same concept as the writeback throttling code, which is watching the overall >> total latency of IO's in a given window and then adjusting the queue depth of >> the group accordingly. This is meant to be a workload protection controller, so >> whoever has the lowest latency target gets the preferential treatment with no >> thought to fairness or proportionality. It is meant to be work conserving, so >> as long as nobody is missing their latency targets the disk is fair game. >> >> We have been testing this in production for several months now to get the >> behavior right and we are finally at the point that it is working well in all of >> our test cases. With this patch we protect our main workload (the web server) >> and isolate out the system services (chef/yum/etc). This works well in the >> normal case, smoothing out weird request per second (RPS) dips that we would see >> when one of the system services would run and compete for IO resources. This >> also works incredibly well in the runaway task case. >> >> The runaway task usecase is where we have some task that slowly eats up all of >> the memory on the system (think a memory leak). Previously this sort of >> workload would push the box into a swapping/oom death spiral that was only >> recovered by rebooting the box. With this patchset and proper configuration of >> the memory.low and io.latency controllers we're able to survive this test with a >> at most 20% dip in RPS. > > Is this purely useful for spinning disks, or is there some > applicability to SSDs and perhaps other storage devices? Some > discussion on this topic would be useful. > > Patches 5, 7 & 14 look fine to me - go wild. #14 could do with a > couple of why-we're-doing-this comments, but I say that about > everything ;) I want to queue this up for 4.19 shortly - is the above an acked-by? Andrewed-by? Which do you prefer? :-) -- Jens Axboe
