From: Johannes Weiner <hannes@cmpxchg.org>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
riel@surriel.com, liam@infradead.org, vbabka@kernel.org,
harry@kernel.org, jannh@google.com, lance.yang@linux.dev,
kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev,
baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com,
weixugc@google.com, mhocko@kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] mm: mglru: promote mapped executable folios after first usage
Date: Fri, 17 Jul 2026 14:44:03 +0200 [thread overview]
Message-ID: <20260717124403.GG6843@cmpxchg.org> (raw)
In-Reply-To: <7db4d1975cf04e3e48157f98bdf398565ee189a4.1784268206.git.baolin.wang@linux.alibaba.com>
On Fri, Jul 17, 2026 at 06:05:34PM +0800, Baolin Wang wrote:
> Classical LRU protects mapped executable file folios through commit
> 8cab4754d24a0 ("vmscan: make mapped executable pages the first class
> citizen") and commit c909e99364c8 ("vmscan: activate executable pages
> after first usage"), giving executable code a better chance to stay in
> memory, avoiding IO thrashing and improving workload performance.
>
> However, MGLRU's protection of mapped executable file folios is less
> reliable. Although shrink_folio_list() checks references, the access flag
> of mapped executable file folios may have already been checked and
> cleared by lru_gen_look_around() or walk_mm(). Additionally,
> folio_update_gen() or lru_gen_set_refs() only sets the 'PG_referenced'
> flag for mapped executable file folios, which causes shrink_folio_list()
> to ignore the first usage of these mapped executable file folios and
> reclaim them easily.
>
> Follow the classical LRU's logic, promoting mapped executable file folios
> after their first usage in folio_update_gen() and lru_gen_set_refs(),
> giving executable code a better chance to stay in memory.
>
> On my 32-core Arm machine, with the memcg limit set to 2G, running
> 'make -j32' to build kernel showed some improvement in sys time.
>
> base patched
> 9248.543s 7861.579s
>
> While we are at it, introduce a new helper to check mapped executable
> file folios.
>
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Both patches contained herein look good:
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
[ Sorry ;-) Please don't mix refactoring work with functional
changes. It's difficult to look through a sequence of diff hunks
with more than one review narrative interleaved. ]
> ---
> mm/vmscan.c | 47 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 31 insertions(+), 16 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index de62899c108d..1040bf9f96e8 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -268,6 +268,12 @@ static int sc_swappiness(struct scan_control *sc, struct mem_cgroup *memcg)
> }
> #endif
>
> +static inline bool is_exec_file_folio(const struct folio *folio,
> + const vma_flags_t *vma_flags)
> +{
> + return vma_flags_test(vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio);
> +}
> +
> static void set_task_reclaim_state(struct task_struct *task,
> struct reclaim_state *rs)
> {
> @@ -835,11 +841,15 @@ enum folio_references {
> * with PG_active set. In contrast, the aging (page table walk) path uses
> * folio_update_gen().
> */
> -static bool lru_gen_set_refs(struct folio *folio)
> +static bool lru_gen_set_refs(struct folio *folio, const vma_flags_t *vma_flags)
> {
> /* see the comment on LRU_REFS_FLAGS */
> if (!folio_test_referenced(folio) && !folio_test_workingset(folio)) {
> set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
> + /* Activate file-backed executable folios after first usage. */
> + if (is_exec_file_folio(folio, vma_flags))
> + return true;
> +
> return false;
> }
>
> @@ -851,7 +861,7 @@ static bool lru_gen_set_refs(struct folio *folio)
> return true;
> }
> #else
> -static bool lru_gen_set_refs(struct folio *folio)
> +static bool lru_gen_set_refs(struct folio *folio, const vma_flags_t *vma_flags)
> {
> return false;
> }
> @@ -886,7 +896,7 @@ static enum folio_references folio_check_references(struct folio *folio,
> if (!referenced_ptes)
> return FOLIOREF_RECLAIM;
>
> - return lru_gen_set_refs(folio) ? FOLIOREF_ACTIVATE : FOLIOREF_KEEP;
> + return lru_gen_set_refs(folio, &vma_flags) ? FOLIOREF_ACTIVATE : FOLIOREF_KEEP;
> }
>
> referenced_folio = folio_test_clear_referenced(folio);
> @@ -914,7 +924,7 @@ static enum folio_references folio_check_references(struct folio *folio,
> /*
> * Activate file-backed executable folios after first usage.
> */
> - if (vma_flags_test(&vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio))
> + if (is_exec_file_folio(folio, &vma_flags))
> return FOLIOREF_ACTIVATE;
>
> return FOLIOREF_KEEP;
> @@ -2119,7 +2129,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> * IO, plus JVM can create lots of anon VM_EXEC folios,
> * so we ignore them here.
> */
> - if (vma_flags_test(&vma_flags, VMA_EXEC_BIT) && folio_is_file_lru(folio)) {
> + if (is_exec_file_folio(folio, &vma_flags)) {
> nr_rotated += folio_nr_pages(folio);
> list_add(&folio->lru, &l_active);
> continue;
> @@ -3188,7 +3198,7 @@ static bool positive_ctrl_err(struct ctrl_pos *sp, struct ctrl_pos *pv)
> ******************************************************************************/
>
> /* promote pages accessed through page tables */
> -static int folio_update_gen(struct folio *folio, int gen)
> +static int folio_update_gen(struct folio *folio, int gen, const vma_flags_t *vma_flags)
> {
> unsigned long new_flags, old_flags = READ_ONCE(folio->flags.f);
>
> @@ -3196,10 +3206,15 @@ static int folio_update_gen(struct folio *folio, int gen)
>
> /* see the comment on LRU_REFS_FLAGS */
> if (!folio_test_referenced(folio) && !folio_test_workingset(folio)) {
> + /* Activate file-backed executable folios after first usage. */
> + if (is_exec_file_folio(folio, vma_flags))
> + goto promote;
> +
> set_mask_bits(&folio->flags.f, LRU_REFS_MASK, BIT(PG_referenced));
> return -1;
> }
>
> +promote:
> do {
> /* lru_gen_del_folio() has isolated this page? */
> if (!(old_flags & LRU_GEN_MASK))
> @@ -3428,8 +3443,8 @@ static bool suitable_to_scan(int total, int young)
> return young * n >= total;
> }
>
> -static void walk_update_folio(struct lru_gen_mm_walk *walk, struct folio *folio,
> - int new_gen, bool dirty)
> +static void walk_update_folio(struct lru_gen_mm_walk *walk, struct vm_area_struct *vma,
> + struct folio *folio, int new_gen, bool dirty)
> {
> int old_gen;
>
> @@ -3442,10 +3457,10 @@ static void walk_update_folio(struct lru_gen_mm_walk *walk, struct folio *folio,
> folio_mark_dirty(folio);
>
> if (walk) {
> - old_gen = folio_update_gen(folio, new_gen);
> + old_gen = folio_update_gen(folio, new_gen, &vma->flags);
> if (old_gen >= 0 && old_gen != new_gen)
> update_batch_size(walk, folio, old_gen, new_gen);
> - } else if (lru_gen_set_refs(folio)) {
> + } else if (lru_gen_set_refs(folio, &vma->flags)) {
> old_gen = folio_lru_gen(folio);
> if (old_gen >= 0 && old_gen != new_gen)
> folio_activate(folio);
> @@ -3518,7 +3533,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> continue;
>
> if (last != folio) {
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, args->vma, last, gen, dirty);
>
> last = folio;
> dirty = false;
> @@ -3531,7 +3546,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
> walk->mm_stats[MM_LEAF_YOUNG] += nr;
> }
>
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, args->vma, last, gen, dirty);
> last = NULL;
>
> if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end))
> @@ -3609,7 +3624,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
> goto next;
>
> if (last != folio) {
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, vma, last, gen, dirty);
>
> last = folio;
> dirty = false;
> @@ -3623,7 +3638,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm_area
> i = i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1;
> } while (i <= MIN_LRU_BATCH);
>
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, vma, last, gen, dirty);
>
> lazy_mmu_mode_disable();
> spin_unlock(ptl);
> @@ -4258,7 +4273,7 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw, unsigned int nr)
> continue;
>
> if (last != folio) {
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, vma, last, gen, dirty);
>
> last = folio;
> dirty = false;
> @@ -4270,7 +4285,7 @@ bool lru_gen_look_around(struct page_vma_mapped_walk *pvmw, unsigned int nr)
> young += nr;
> }
>
> - walk_update_folio(walk, last, gen, dirty);
> + walk_update_folio(walk, vma, last, gen, dirty);
>
> lazy_mmu_mode_disable();
>
> --
> 2.47.3
>
next prev parent reply other threads:[~2026-07-17 12:44 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-17 10:05 [PATCH v3 0/2] promote mapped executable folios after first usage for MGLRU Baolin Wang
2026-07-17 10:05 ` [PATCH v3 1/2] mm: vmscan: convert folio_referenced() to use vma_flags_t Baolin Wang
2026-07-17 12:34 ` Johannes Weiner
2026-07-17 10:05 ` [PATCH v3 2/2] mm: mglru: promote mapped executable folios after first usage Baolin Wang
2026-07-17 12:44 ` Johannes Weiner [this message]
2026-07-17 12:58 ` Baolin Wang
2026-07-17 17:27 ` [PATCH v3 0/2] promote mapped executable folios after first usage for MGLRU Axel Rasmussen
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