On Wed, Aug 11, 2021 at 03:57:07PM -0400, Waiman Long wrote: > When a user changes cpuset.cpus, each task in a v2 cpuset will be moved > to one of the new cpus if it is not there already. For memory, however, > they won't be migrated to the new nodes when cpuset.mems changes. This is > an inconsistency in behavior. > > In cpuset v1, there is a memory_migrate control file to enable such > behavior by setting the CS_MEMORY_MIGRATE flag. Make it the default > for cpuset v2 so that we have a consistent set of behavior for both > cpus and memory. > > There is certainly a cost to make memory migration the default, but it > is a one time cost that shouldn't really matter as long as cpuset.mems > isn't changed frequenty. Update the cgroup-v2.rst file to document the > new behavior and recommend against changing cpuset.mems frequently. > > Since there won't be any concurrent access to the newly allocated cpuset > structure in cpuset_css_alloc(), we can use the cheaper non-atomic > __set_bit() instead of the more expensive atomic set_bit(). > > Signed-off-by: Waiman Long <longman@xxxxxxxxxx> LGTM. Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
