On 8/17/23 04:40, Gang Li wrote:
Since __GFP_HARDWALL is set as long as cpuset is enabled, I think we can use it to determine if we are under the constraint of CPUSET. But I have a question: Why we always set __GFP_HARDWALL when cpuset is enabled, regardless of the value of cpuset.mem_hardwall?
There is no direct dependency between cpuset.mem_hardwall and the __GFP_HARDWALL flag. When cpuset is enabled, all user memory allocation should be subjected to the cpuset memory constraint. In the case of non-user memory allocation, it can fall back to to the node mask of an ancestor up to the root cgroup, i.e. all memory nodes. cpuset.mem_hardwall enables a barrier to this upward search.
Note that cpuset.mem_hardwall is a v1 feature that is not available in cgroup v2.
Cheers, Longman
