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mm: multi-gen LRU: simplify lru_gen_look_around()

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Update the folio generation in place with or without
current->reclaim_state->mm_walk.  The LRU lock is held for longer, if
mm_walk is NULL and the number of folios to update is more than
PAGEVEC_SIZE.

This causes a measurable regression from the LRU lock contention during a
microbencmark.  But a tiny regression is not worth the complexity.

Link: https://lkml.kernel.org/r/20230118001827.1040870-8-talumbau@google.com
Signed-off-by: T.J. Alumbaugh <talumbau@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
T.J. Alumbaugh 2023-01-18 00:18:27 +00:00 committed by Andrew Morton
parent b5ff413361
commit abf086721a
1 changed files with 23 additions and 50 deletions
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73
mm/vmscan.c
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@ -4587,13 +4587,12 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
{
int i;
pte_t *pte;
unsigned long start;
unsigned long end;
unsigned long addr;
struct lru_gen_mm_walk *walk;
int young = 0;
unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)] = {};
pte_t *pte = pvmw->pte;
unsigned long addr = pvmw->address;
struct folio *folio = pfn_folio(pvmw->pfn);
struct mem_cgroup *memcg = folio_memcg(folio);
struct pglist_data *pgdat = folio_pgdat(folio);
@ -4610,25 +4609,28 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
/* avoid taking the LRU lock under the PTL when possible */
walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
start = max(pvmw->address & PMD_MASK, pvmw->vma->vm_start);
end = min(pvmw->address | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1;
start = max(addr & PMD_MASK, pvmw->vma->vm_start);
end = min(addr | ~PMD_MASK, pvmw->vma->vm_end - 1) + 1;
if (end - start > MIN_LRU_BATCH * PAGE_SIZE) {
if (pvmw->address - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
if (addr - start < MIN_LRU_BATCH * PAGE_SIZE / 2)
end = start + MIN_LRU_BATCH * PAGE_SIZE;
else if (end - pvmw->address < MIN_LRU_BATCH * PAGE_SIZE / 2)
else if (end - addr < MIN_LRU_BATCH * PAGE_SIZE / 2)
start = end - MIN_LRU_BATCH * PAGE_SIZE;
else {
start = pvmw->address - MIN_LRU_BATCH * PAGE_SIZE / 2;
end = pvmw->address + MIN_LRU_BATCH * PAGE_SIZE / 2;
start = addr - MIN_LRU_BATCH * PAGE_SIZE / 2;
end = addr + MIN_LRU_BATCH * PAGE_SIZE / 2;
}
}
pte = pvmw->pte - (pvmw->address - start) / PAGE_SIZE;
/* folio_update_gen() requires stable folio_memcg() */
if (!mem_cgroup_trylock_pages(memcg))
return;
rcu_read_lock();
arch_enter_lazy_mmu_mode();
pte -= (addr - start) / PAGE_SIZE;
for (i = 0, addr = start; addr != end; i++, addr += PAGE_SIZE) {
unsigned long pfn;
@ -4653,56 +4655,27 @@ void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
!folio_test_swapcache(folio)))
folio_mark_dirty(folio);
if (walk) {
old_gen = folio_update_gen(folio, new_gen);
if (old_gen >= 0 && old_gen != new_gen)
update_batch_size(walk, folio, old_gen, new_gen);
continue;
}
old_gen = folio_lru_gen(folio);
if (old_gen < 0)
folio_set_referenced(folio);
else if (old_gen != new_gen)
__set_bit(i, bitmap);
folio_activate(folio);
}
arch_leave_lazy_mmu_mode();
rcu_read_unlock();
mem_cgroup_unlock_pages();
/* feedback from rmap walkers to page table walkers */
if (suitable_to_scan(i, young))
update_bloom_filter(lruvec, max_seq, pvmw->pmd);
if (!walk && bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) {
for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
folio = pfn_folio(pte_pfn(pte[i]));
folio_activate(folio);
}
return;
}
/* folio_update_gen() requires stable folio_memcg() */
if (!mem_cgroup_trylock_pages(memcg))
return;
if (!walk) {
spin_lock_irq(&lruvec->lru_lock);
new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq);
}
for_each_set_bit(i, bitmap, MIN_LRU_BATCH) {
folio = pfn_folio(pte_pfn(pte[i]));
if (folio_memcg_rcu(folio) != memcg)
continue;
old_gen = folio_update_gen(folio, new_gen);
if (old_gen < 0 || old_gen == new_gen)
continue;
if (walk)
update_batch_size(walk, folio, old_gen, new_gen);
else
lru_gen_update_size(lruvec, folio, old_gen, new_gen);
}
if (!walk)
spin_unlock_irq(&lruvec->lru_lock);
mem_cgroup_unlock_pages();
}
/******************************************************************************