[PATCH v1 5/6] memcg-v1: no need for memcg locking for MGLRU

Shakeel Butt
2024-10-25T01:23:45Z

While updating the generation of the folios, MGLRU requires that the
folio's memcg association remains stable. With the charge migration
deprecated, there is no need for MGLRU to acquire locks to keep the
folio and memcg association stable.

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
---
mm/vmscan.c | 11 -----------
1 file changed, 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 29c098790b01..fd7171658b63 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3662,10 +3662,6 @@ static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
if (walk->seq != max_seq)
break;

- /* folio_update_gen() requires stable folio_memcg() */
- if (!mem_cgroup_trylock_pages(memcg))
- break;
-
/* the caller might be holding the lock for write */
if (mmap_read_trylock(mm)) {
err = walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, walk);
@@ -3673,8 +3669,6 @@ static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
mmap_read_unlock(mm);
}

- mem_cgroup_unlock_pages();
-
if (walk->batched) {
spin_lock_irq(&lruvec->lru_lock);
reset_batch_size(walk);
@@ -4096,10 +4090,6 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
}
}

- /* folio_update_gen() requires stable folio_memcg() */
- if (!mem_cgroup_trylock_pages(memcg))
- return true;
-
arch_enter_lazy_mmu_mode();

pte -= (addr - start) / PAGE_SIZE;
@@ -4144,7 +4134,6 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
}

arch_leave_lazy_mmu_mode();
- mem_cgroup_unlock_pages();

/* feedback from rmap walkers to page table walkers */
if (mm_state && suitable_to_scan(i, young))
--
2.43.5