On 05/01/2018 03:51 PM, Tejun Heo wrote: > Hello, Waiman. > > Sorry about the delay. > > On Thu, Apr 19, 2018 at 09:47:03AM -0400, Waiman Long wrote: >> With the addition of "cpuset.cpus.isolated", it makes sense to add the >> restriction that load balancing can only be turned off if the CPUs in >> the isolated cpuset are subset of "cpuset.cpus.isolated". >> >> Signed-off-by: Waiman Long <longman@xxxxxxxxxx> >> --- >> Documentation/cgroup-v2.txt | 7 ++++--- >> kernel/cgroup/cpuset.c | 29 ++++++++++++++++++++++++++--- >> 2 files changed, 30 insertions(+), 6 deletions(-) >> >> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt >> index 8d89dc2..c4227ee 100644 >> --- a/Documentation/cgroup-v2.txt >> +++ b/Documentation/cgroup-v2.txt >> @@ -1554,9 +1554,10 @@ Cpuset Interface Files >> and will not be moved to other CPUs. >> >> This flag is hierarchical and is inherited by child cpusets. It >> - can be turned off only when the CPUs in this cpuset aren't >> - listed in the cpuset.cpus of other sibling cgroups, and all >> - the child cpusets, if present, have this flag turned off. >> + can be explicitly turned off only when it is a direct child of >> + the root cgroup and the CPUs in this cpuset are subset of the >> + root's "cpuset.cpus.isolated". Moreover, the CPUs cannot be >> + listed in the "cpuset.cpus" of other sibling cgroups. > It is a little bit convoluted that the isolation requires coordination > among root's isolated file and the first-level children's cpus file > and the flag. Maybe I'm missing something but can't we do something > like the following? > > * Add isolated flag file, which can only be modified on empty (in > terms of cpus) first level children. > > * Once isolated flag is set, CPUs can only be added to the cpus file > iff they aren't being used by anyone else and automatically become > isolated. > > The first level cpus file is owned by the root cgroup anyway, so > there's no danger regarding delegation or whatever and the interface > would be a lot simpler. I think that will work too. We currently don't have a flag to make a file visible on first-level children only, but it shouldn't be hard to make one. Putting CPUs into an isolated child cpuset means removing it from the root's effective CPUs. So I would probably like to expose the read-only cpus.effective in the root cgroup so that we can check changes in the effective cpu list. I will renew the patchset will your suggestion. Thanks, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
