[PATCH v2 0/3] distinct load average per-cpuset

From: Andrea Righi
Date: Sat Oct 20 2012 - 15:06:11 EST

The cpusets subsystem allows to assign a different set of CPUs to a cgroup. A
typical use case is to split large systems in small CPU/memory partitions and
isolate certain users/applications in these subsets of the system.

Sometimes, to have a quick overview of the state of each partition, we may be
interested to get the load average of the CPUs assigned to a particular cpuset,
rather than the global load average of the system.

Proposed solution
The proposal is to add a new file in the cpuset subsystem to report the load
average of the CPUs assinged to a particular cpuset cgroup.


# echo 0-1 > /sys/fs/cgroup/cpuset/foo/cpuset.cpus
# echo 2-3 > /sys/fs/cgroup/cpuset/bar/cpuset.cpus

# echo $$ > /sys/fs/cgroup/cpuset/foo/tasks
# for i in `seq 4`; do yes > /dev/null & done

... after ~5mins ...

# cat /proc/loadavg /sys/fs/cgroup/cpuset/{foo,bar}/cpuset.loadavg
3.99 2.66 1.24 6/377 2855
3.98 2.64 1.20
0.01 0.02 0.04

In this case we can easily find that the cpuset "foo" is the most busy in the

ChangeLog v1->v2:
- convert rq->nr_uninterruptible to a percpu variable
- fix nr_uninterruptible accounting in the wakeup/sleep paths
- use DEFINE_PER_CPU() instead of NR_CPUS arrays
- in patch 2/3 add a comment to explain the validity of evaluating the cpuset
load average as the sum of the individual per-cpu load averages

[ Thanks to Peter Z. for the review and suggestions of v1 ]

- report nr_running and nr_threads in cpuset.loadavg, producing the same
output as /proc/loadavg; in this way we could do nice things like, for
example, "mount --bind cpuset.loadavg /proc/loadavg" in a new mount
namespace for a specific user that we want to isolate into a specific
cpuset cgroup, etc...

[PATCH v2 1/3] sched: introduce distinct per-cpu load average
[PATCH v2 2/3] cpusets: add load avgerage interface
[PATCH v2 3/3] cpusets: add documentation of the loadavg file

Documentation/cgroups/cpusets.txt | 1 +
include/linux/sched.h | 6 ++
kernel/cpuset.c | 108 +++++++++++++++++++++++++++++++++++
kernel/sched/core.c | 112 +++++++++++++++++++++++++++++++------
kernel/sched/debug.c | 3 +-
kernel/sched/sched.h | 8 +--
6 files changed, 214 insertions(+), 24 deletions(-)
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