tree d852c95da89a6c385df27190a4f720a899f35361
parent 0d054fc5d7775a7b38e33fe243fdabdf4fada8fa
author Suren Baghdasaryan <surenb@google.com> 1621886019 -0700
committer Suren Baghdasaryan <surenb@google.com> 1624473335 +0000

FROMGIT: cgroup: make per-cgroup pressure stall tracking configurable

PSI accounts stalls for each cgroup separately and aggregates it at each
level of the hierarchy. This causes additional overhead with psi_avgs_work
being called for each cgroup in the hierarchy. psi_avgs_work has been
highly optimized, however on systems with large number of cgroups the
overhead becomes noticeable.
Systems which use PSI only at the system level could avoid this overhead
if PSI can be configured to skip per-cgroup stall accounting.
Add "cgroup_disable=pressure" kernel command-line option to allow
requesting system-wide only pressure stall accounting. When set, it
keeps system-wide accounting under /proc/pressure/ but skips accounting
for individual cgroups and does not expose PSI nodes in cgroup hierarchy.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Link:  https://lore.kernel.org/patchwork/patch/1435705
(cherry picked from commit 3958e2d0c34e18c41b60dc01832bd670a59ef70f
 https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git tj)

Bug: 178872719
Bug: 191734423
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: Ifc8fbc52f9a1131d7c2668edbb44c525c76c3360