On 11/11/25 10:33 PM, Chen Ridong wrote:
On 2025/11/12 10:11, Sun Shaojie wrote:
Hello Shaojie,
Currently, when a non-exclusive cpuset's "cpuset.cpus" overlaps with a
partitioned sibling, the sibling's partition state becomes invalid.
However, this invalidation is often unnecessary.
This can be observed in specific configuration sequences:
Case 1: Partition created first, then non-exclusive cpuset overlaps
#1> mkdir -p /sys/fs/cgroup/A1
#2> echo "0-1" > /sys/fs/cgroup/A1/cpuset.cpus
#3> echo "root" > /sys/fs/cgroup/A1/cpuset.cpus.partition
#4> mkdir -p /sys/fs/cgroup/B1
#5> echo "0-3" > /sys/fs/cgroup/B1/cpuset.cpus
// A1's partition becomes "root invalid" - this is unnecessary
Case 2: Non-exclusive cpuset exists first, then partition created
#1> mkdir -p /sys/fs/cgroup/B1
#2> echo "0-1" > /sys/fs/cgroup/B1/cpuset.cpus
#3> mkdir -p /sys/fs/cgroup/A1
#4> echo "0-1" > /sys/fs/cgroup/A1/cpuset.cpus
#5> echo "root" > /sys/fs/cgroup/A1/cpuset.cpus.partition
// A1's partition becomes "root invalid" - this is unnecessary
In Case 1, the effective CPU mask of B1 can differ from its requested
mask. B1 can use CPUs 2-3 which don't overlap with A1's exclusive
CPUs (0-1), thus not violating A1's exclusivity requirement.
In Case 2, B1 can inherit the effective CPUs from its parent, so there
is no need to invalidate A1's partition state.
This patch relaxes the overlap check to only consider conflicts between
partitioned siblings, not between a partitioned cpuset and a regular
non-exclusive one.
The current cgroup v2 exclusive cpuset behavior follows the v1 behavior
of cpuset.cpus.exclusive flag. Even if we want to relax the cgroup v2
behavior, we will still need to maintain the v1 behavior as we want to
minimize any changes to cgroup v1. IOW, we have to gate this change
specific to v2.
Cheers,
Longman
