cgroup, sched: let cpu serve the same files as cpuacct
cpuacct being on a separate hierarchy is one of the main cgroup
related complaints from scheduler side and the consensus seems to be
* Allowing cpuacct to be a separate controller was a mistake. In
general multiple controllers on the same type of resource should be
avoided, especially accounting-only ones.
* Statistics provided by cpuacct are useful and should instead be
served by cpu.
This patch makes cpu maintain and serve all cpuacct.* files and make
cgroup core ignore cpuacct if it's co-mounted with cpu. This is a
step in deprecating cpuacct. The next patch will allow disabling or
dropping cpuacct without affecting userland too much.
Note that this creates some discrepancies in /proc/cgroups and
/proc/PID/cgroup. The co-mounted cpuacct won't be reflected correctly
there. cpuacct will eventually be removed completely probably except
for the statistics filenames and I'd like to keep the amount of
compatbility hackery to minimum as much as possible.
The cpu statistics implementation isn't optimized in any way. It's
mostly verbatim copy from cpuacct. The goal is allowing quick
disabling and removal of CONFIG_CGROUP_CPUACCT and creating a base on
top of which cpu can implement proper optimization.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Cc: Dave Jones <davej@redhat.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Paul Turner <pjt@google.com>
6 files changed
