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Fri, 17 Jul 2026 05:44:05 -0700 (PDT) Date: Fri, 17 Jul 2026 14:44:03 +0200 From: Johannes Weiner To: Baolin Wang 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 Message-ID: <20260717124403.GG6843@cmpxchg.org> References: <7db4d1975cf04e3e48157f98bdf398565ee189a4.1784268206.git.baolin.wang@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 Both patches contained herein look good: Acked-by: Johannes Weiner Acked-by: Johannes Weiner [ 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 >