| From: Joshua Hahn <joshua.hahnjy@gmail.com> |
| Subject: mm/mempolicy: skip unnecessary synchronize_rcu() |
| Date: Mon, 2 Jun 2025 09:23:40 -0700 |
| |
| By unconditionally setting wi_state to NULL and conditionally calling |
| synchronize_rcu(), we can save an unncessary call when there is no |
| old_wi_state. |
| |
| Link: https://lkml.kernel.org/r/20250602162345.2595696-2-joshua.hahnjy@gmail.com |
| Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com> |
| Suggested-by: David Hildenbrand <david@redhat.com> |
| Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com> |
| Cc: Alistair Popple <apopple@nvidia.com> |
| Cc: Byungchul Park <byungchul@sk.com> |
| Cc: Gregory Price <gourry@gourry.net> |
| Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> |
| Cc: kernel test robot <lkp@intel.com> |
| Cc: Mathew Brost <matthew.brost@intel.com> |
| Cc: Rakie Kim <rakie.kim@sk.com> |
| Cc: Zi Yan <ziy@nvidia.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/mempolicy.c | 13 +++++-------- |
| 1 file changed, 5 insertions(+), 8 deletions(-) |
| |
| --- a/mm/mempolicy.c~mm-mempolicy-skip-unnecessary-synchronize_rcu |
| +++ a/mm/mempolicy.c |
| @@ -3703,18 +3703,15 @@ static void wi_state_free(void) |
| struct weighted_interleave_state *old_wi_state; |
| |
| mutex_lock(&wi_state_lock); |
| - |
| old_wi_state = rcu_dereference_protected(wi_state, |
| lockdep_is_held(&wi_state_lock)); |
| - if (!old_wi_state) { |
| - mutex_unlock(&wi_state_lock); |
| - return; |
| - } |
| - |
| rcu_assign_pointer(wi_state, NULL); |
| mutex_unlock(&wi_state_lock); |
| - synchronize_rcu(); |
| - kfree(old_wi_state); |
| + |
| + if (old_wi_state) { |
| + synchronize_rcu(); |
| + kfree(old_wi_state); |
| + } |
| } |
| |
| static struct kobj_attribute wi_auto_attr = |
| _ |
