Messages in this thread | | | Date | Mon, 1 Jun 2020 16:42:14 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH 2/2 blk-cgroup/for-5.8] blk-cgroup: show global disk stats in root cgroup io.stat |
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On Mon, Jun 01, 2020 at 01:12:05PM -0700, Boris Burkov wrote: > In order to improve consistency and usability in cgroup stat accounting, > we would like to support the root cgroup's io.stat. > > Since the root cgroup has processes doing io even if the system has no > explicitly created cgroups, we need to be careful to avoid overhead in > that case. For that reason, the rstat algorithms don't handle the root > cgroup, so just turning the file on wouldn't give correct statistics. > > To get around this, we simulate flushing the iostat struct by filling it > out directly from global disk stats. The result is a root cgroup io.stat > file consistent with both /proc/diskstats and io.stat. > > Note that in order to collect the disk stats, we needed to iterate over > devices. To facilitate that, we had to change the linkage of a disk_type > to external so that it can be used from blk-cgroup.c to iterate over > disks. > > Signed-off-by: Boris Burkov <boris@bur.io> > Suggested-by: Tejun Heo <tj@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Thanks.
-- tejun
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