The patch titled
Subject: mm: multi-gen LRU: simplify lru_gen_look_around()
has been added to the -mm mm-unstable branch. Its filename is
mm-multi-gen-lru-simplify-lru_gen_look_around.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-multi-gen-lru-simplify-lru_gen_look_around.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: "T.J. Alumbaugh" <talumbau@xxxxxxxxxx>
Subject: mm: multi-gen LRU: simplify lru_gen_look_around()
Date: Wed, 18 Jan 2023 00:18:27 +0000
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@xxxxxxxxxx
Signed-off-by: T.J. Alumbaugh <talumbau@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/vmscan.c~mm-multi-gen-lru-simplify-lru_gen_look_around
+++ a/mm/vmscan.c
@@ -4587,13 +4587,12 @@ static void lru_gen_age_node(struct pgli
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
/* 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
!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();
}
/******************************************************************************
_
Patches currently in -mm which might be from talumbau@xxxxxxxxxx are
mm-multi-gen-lru-section-for-working-set-protection.patch
mm-multi-gen-lru-section-for-rmap-pt-walk-feedback.patch
mm-multi-gen-lru-section-for-bloom-filters.patch
mm-multi-gen-lru-section-for-memcg-lru.patch
mm-multi-gen-lru-improve-lru_gen_exit_memcg.patch
mm-multi-gen-lru-improve-walk_pmd_range.patch
mm-multi-gen-lru-simplify-lru_gen_look_around.patch
