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AJvYcCXf0zjWEnL3tGVUjKiDXgCG6jlB2PVYby8rwAWaKsTIMU9VCACqA+IElsxXoynz//3k3MTJdRlhx8iJ75w=@vger.kernel.org X-Gm-Message-State: AOJu0Yyoox/uIKPdTeVgFAFQrSeAq1SwIb5yInmM+viAGhmlvusYVpwf HWN9BfGYVC10DDqpCxtHviEpeilDMC03suYkPElJ9vD7Lnf/8dFQMIYLLZ8MC+1B/2C7DrMqYFe RMYaqS5Sgxg== X-Google-Smtp-Source: AGHT+IFxcf1ulizGHCmrAYuaueILB7KnJ+mFxdngS8qoVQOFjaGknbkRH4uweWaOG90A2VClWCEi/Qzqir1kug== X-Received: from pfbhq26.prod.google.com ([2002:a05:6a00:681a:b0:736:6fb6:7fc]) (user=kinseyho job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3a07:b0:736:3768:6d74 with SMTP id d2e1a72fcca58-7390598e60amr22559759b3a.7.1742853791050; Mon, 24 Mar 2025 15:03:11 -0700 (PDT) Date: Mon, 24 Mar 2025 15:03:00 -0700 In-Reply-To: <20250324220301.1273038-1-kinseyho@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250324220301.1273038-1-kinseyho@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250324220301.1273038-2-kinseyho@google.com> Subject: [RFC PATCH v1 1/2] mm: mglru: generalize page table walk From: Kinsey Ho To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: yuanchu@google.com, AneeshKumar.KizhakeVeetil@arm.com, Hasan.Maruf@amd.com, Jonathan.Cameron@huawei.com, Michael.Day@amd.com, akpm@linux-foundation.org, dave.hansen@intel.com, david@redhat.com, feng.tang@intel.com, gourry@gourry.net, hannes@cmpxchg.org, honggyu.kim@sk.com, hughd@google.com, jhubbard@nvidia.com, k.shutemov@gmail.com, kbusch@meta.com, kmanaouil.dev@gmail.com, leesuyeon0506@gmail.com, leillc@google.com, liam.howlett@oracle.com, mgorman@techsingularity.net, mingo@redhat.com, nadav.amit@gmail.com, nphamcs@gmail.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, rppt@kernel.org, shivankg@amd.com, shy828301@gmail.com, sj@kernel.org, vbabka@suse.cz, weixugc@google.com, willy@infradead.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, hyeonggon.yoo@sk.com, bharata@amd.com, Kinsey Ho Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Refactor the existing MGLRU page table walking logic to make it resumable. Additionally, introduce two hooks into the MGLRU page table walk: accessed callback and flush callback. The accessed callback is called for each accessed page detected via the scanned accessed bit. The flush callback is called when the accessed callback reports an out of space error. This allows for processing pages in batches for efficiency. With a generalised page table walk, introduce a new scan function which repeatedly scans on the same young generation and does not add a new young generation. Signed-off-by: Kinsey Ho Signed-off-by: Yuanchu Xie --- include/linux/mmzone.h | 5 ++ mm/internal.h | 4 + mm/vmscan.c | 177 ++++++++++++++++++++++++++++++----------- 3 files changed, 140 insertions(+), 46 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index a5c4e789aa55..bab586961a82 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -511,6 +511,8 @@ struct lru_gen_mm_walk { unsigned long seq; /* the next address within an mm to scan */ unsigned long next_addr; + /* called for each accessed pte/pmd */ + int (*accessed_cb)(pfn_t pfn); /* to batch promoted pages */ int nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES]; /* to batch the mm stats */ @@ -518,6 +520,9 @@ struct lru_gen_mm_walk { /* total batched items */ int batched; int swappiness; + /* for the pmd under scanning */ + int nr_young_pte; + int nr_total_pte; bool force_scan; }; =20 diff --git a/mm/internal.h b/mm/internal.h index 20b3535935a3..3bf528af2deb 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -476,6 +476,10 @@ extern unsigned long highest_memmap_pfn; bool folio_isolate_lru(struct folio *folio); void folio_putback_lru(struct folio *folio); extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state = reason); +void set_task_reclaim_state(struct task_struct *task, + struct reclaim_state *rs); +void lru_gen_scan_lruvec(struct lruvec *lruvec, unsigned long seq, + int (*accessed_cb)(pfn_t), void (*flush_cb)(void)); =20 /* * in mm/rmap.c: diff --git a/mm/vmscan.c b/mm/vmscan.c index c767d71c43d7..fb828a429645 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -57,6 +57,7 @@ #include #include #include +#include =20 #include #include @@ -271,7 +272,7 @@ static int sc_swappiness(struct scan_control *sc, struc= t mem_cgroup *memcg) } #endif =20 -static void set_task_reclaim_state(struct task_struct *task, +void set_task_reclaim_state(struct task_struct *task, struct reclaim_state *rs) { /* Check for an overwrite */ @@ -3023,7 +3024,7 @@ static bool iterate_mm_list(struct lru_gen_mm_walk *w= alk, struct mm_struct **ite =20 VM_WARN_ON_ONCE(mm_state->seq + 1 < walk->seq); =20 - if (walk->seq <=3D mm_state->seq) + if (!walk->accessed_cb && walk->seq <=3D mm_state->seq) goto done; =20 if (!mm_state->head) @@ -3452,16 +3453,14 @@ static void walk_update_folio(struct lru_gen_mm_wal= k *walk, struct folio *folio, } } =20 -static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long = end, - struct mm_walk *args) +static int walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long e= nd, + struct mm_walk *args, bool *suitable) { - int i; + int i, err =3D 0; bool dirty; pte_t *pte; spinlock_t *ptl; unsigned long addr; - int total =3D 0; - int young =3D 0; struct folio *last =3D NULL; struct lru_gen_mm_walk *walk =3D args->private; struct mem_cgroup *memcg =3D lruvec_memcg(walk->lruvec); @@ -3471,17 +3470,21 @@ static bool walk_pte_range(pmd_t *pmd, unsigned lon= g start, unsigned long end, pmd_t pmdval; =20 pte =3D pte_offset_map_rw_nolock(args->mm, pmd, start & PMD_MASK, &pmdval= , &ptl); - if (!pte) - return false; + if (!pte) { + *suitable =3D false; + return 0; + } =20 if (!spin_trylock(ptl)) { pte_unmap(pte); - return true; + *suitable =3D true; + return 0; } =20 if (unlikely(!pmd_same(pmdval, pmdp_get_lockless(pmd)))) { pte_unmap_unlock(pte, ptl); - return false; + *suitable =3D false; + return 0; } =20 arch_enter_lazy_mmu_mode(); @@ -3491,7 +3494,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long = start, unsigned long end, struct folio *folio; pte_t ptent =3D ptep_get(pte + i); =20 - total++; + walk->nr_total_pte++; walk->mm_stats[MM_LEAF_TOTAL]++; =20 pfn =3D get_pte_pfn(ptent, args->vma, addr, pgdat); @@ -3515,23 +3518,34 @@ static bool walk_pte_range(pmd_t *pmd, unsigned lon= g start, unsigned long end, if (pte_dirty(ptent)) dirty =3D true; =20 - young++; + walk->nr_young_pte++; walk->mm_stats[MM_LEAF_YOUNG]++; + + if (!walk->accessed_cb) + continue; + + err =3D walk->accessed_cb(pfn_to_pfn_t(pfn)); + if (err) { + walk->next_addr =3D addr + PAGE_SIZE; + break; + } } =20 walk_update_folio(walk, last, gen, dirty); last =3D NULL; =20 - if (i < PTRS_PER_PTE && get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &= end)) + if (!err && i < PTRS_PER_PTE && + get_next_vma(PMD_MASK, PAGE_SIZE, args, &start, &end)) goto restart; =20 arch_leave_lazy_mmu_mode(); pte_unmap_unlock(pte, ptl); =20 - return suitable_to_scan(total, young); + *suitable =3D suitable_to_scan(walk->nr_total_pte, walk->nr_young_pte); + return err; } =20 -static void walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct v= m_area_struct *vma, +static int walk_pmd_range_locked(pud_t *pud, unsigned long addr, struct vm= _area_struct *vma, struct mm_walk *args, unsigned long *bitmap, unsigned long *first) { int i; @@ -3544,6 +3558,7 @@ static void walk_pmd_range_locked(pud_t *pud, unsigne= d long addr, struct vm_area struct pglist_data *pgdat =3D lruvec_pgdat(walk->lruvec); DEFINE_MAX_SEQ(walk->lruvec); int gen =3D lru_gen_from_seq(max_seq); + int err =3D 0; =20 VM_WARN_ON_ONCE(pud_leaf(*pud)); =20 @@ -3551,13 +3566,13 @@ static void walk_pmd_range_locked(pud_t *pud, unsig= ned long addr, struct vm_area if (*first =3D=3D -1) { *first =3D addr; bitmap_zero(bitmap, MIN_LRU_BATCH); - return; + return 0; } =20 i =3D addr =3D=3D -1 ? 0 : pmd_index(addr) - pmd_index(*first); if (i && i <=3D MIN_LRU_BATCH) { __set_bit(i - 1, bitmap); - return; + return 0; } =20 pmd =3D pmd_offset(pud, *first); @@ -3607,6 +3622,16 @@ static void walk_pmd_range_locked(pud_t *pud, unsign= ed long addr, struct vm_area dirty =3D true; =20 walk->mm_stats[MM_LEAF_YOUNG]++; + if (!walk->accessed_cb) + goto next; + + err =3D walk->accessed_cb(pfn_to_pfn_t(pfn)); + if (err) { + i =3D find_next_bit(bitmap, MIN_LRU_BATCH, i) + 1; + + walk->next_addr =3D (*first & PMD_MASK) + i * PMD_SIZE; + break; + } next: i =3D i > MIN_LRU_BATCH ? 0 : find_next_bit(bitmap, MIN_LRU_BATCH, i) + = 1; } while (i <=3D MIN_LRU_BATCH); @@ -3617,9 +3642,10 @@ static void walk_pmd_range_locked(pud_t *pud, unsign= ed long addr, struct vm_area spin_unlock(ptl); done: *first =3D -1; + return err; } =20 -static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long = end, +static int walk_pmd_range(pud_t *pud, unsigned long start, unsigned long e= nd, struct mm_walk *args) { int i; @@ -3631,6 +3657,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long = start, unsigned long end, unsigned long first =3D -1; struct lru_gen_mm_walk *walk =3D args->private; struct lru_gen_mm_state *mm_state =3D get_mm_state(walk->lruvec); + int err =3D 0; =20 VM_WARN_ON_ONCE(pud_leaf(*pud)); =20 @@ -3644,6 +3671,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long = start, unsigned long end, /* walk_pte_range() may call get_next_vma() */ vma =3D args->vma; for (i =3D pmd_index(start), addr =3D start; addr !=3D end; i++, addr =3D= next) { + bool suitable; pmd_t val =3D pmdp_get_lockless(pmd + i); =20 next =3D pmd_addr_end(addr, end); @@ -3660,7 +3688,10 @@ static void walk_pmd_range(pud_t *pud, unsigned long= start, unsigned long end, walk->mm_stats[MM_LEAF_TOTAL]++; =20 if (pfn !=3D -1) - walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); + err =3D walk_pmd_range_locked(pud, addr, vma, args, + bitmap, &first); + if (err) + return err; continue; } =20 @@ -3669,33 +3700,50 @@ static void walk_pmd_range(pud_t *pud, unsigned lon= g start, unsigned long end, if (!pmd_young(val)) continue; =20 - walk_pmd_range_locked(pud, addr, vma, args, bitmap, &first); + err =3D walk_pmd_range_locked(pud, addr, vma, args, + bitmap, &first); + if (err) + return err; } =20 if (!walk->force_scan && !test_bloom_filter(mm_state, walk->seq, pmd + i= )) continue; =20 + err =3D walk_pte_range(&val, addr, next, args, &suitable); + if (err && walk->next_addr < next && first =3D=3D -1) + return err; + + walk->nr_total_pte =3D 0; + walk->nr_young_pte =3D 0; + walk->mm_stats[MM_NONLEAF_FOUND]++; =20 - if (!walk_pte_range(&val, addr, next, args)) - continue; + if (!suitable) + goto next; =20 walk->mm_stats[MM_NONLEAF_ADDED]++; =20 /* carry over to the next generation */ update_bloom_filter(mm_state, walk->seq + 1, pmd + i); +next: + if (err) { + walk->next_addr =3D first; + return err; + } } =20 - walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first); + err =3D walk_pmd_range_locked(pud, -1, vma, args, bitmap, &first); =20 - if (i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &start, &e= nd)) + if (!err && i < PTRS_PER_PMD && get_next_vma(PUD_MASK, PMD_SIZE, args, &s= tart, &end)) goto restart; + + return err; } =20 static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long e= nd, struct mm_walk *args) { - int i; + int i, err; pud_t *pud; unsigned long addr; unsigned long next; @@ -3713,7 +3761,9 @@ static int walk_pud_range(p4d_t *p4d, unsigned long s= tart, unsigned long end, if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val))) continue; =20 - walk_pmd_range(&val, addr, next, args); + err =3D walk_pmd_range(&val, addr, next, args); + if (err) + return err; =20 if (need_resched() || walk->batched >=3D MAX_LRU_BATCH) { end =3D (addr | ~PUD_MASK) + 1; @@ -3734,40 +3784,48 @@ static int walk_pud_range(p4d_t *p4d, unsigned long= start, unsigned long end, return -EAGAIN; } =20 -static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk) +static int try_walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk) { + int err; static const struct mm_walk_ops mm_walk_ops =3D { .test_walk =3D should_skip_vma, .p4d_entry =3D walk_pud_range, .walk_lock =3D PGWALK_RDLOCK, }; - int err; struct lruvec *lruvec =3D walk->lruvec; =20 - walk->next_addr =3D FIRST_USER_ADDRESS; + DEFINE_MAX_SEQ(lruvec); =20 - do { - DEFINE_MAX_SEQ(lruvec); + err =3D -EBUSY; =20 - err =3D -EBUSY; + /* another thread might have called inc_max_seq() */ + if (walk->seq !=3D max_seq) + return err; =20 - /* another thread might have called inc_max_seq() */ - if (walk->seq !=3D max_seq) - break; + /* the caller might be holding the lock for write */ + if (mmap_read_trylock(mm)) { + err =3D walk_page_range(mm, walk->next_addr, ULONG_MAX, + &mm_walk_ops, walk); =20 - /* the caller might be holding the lock for write */ - if (mmap_read_trylock(mm)) { - err =3D walk_page_range(mm, walk->next_addr, ULONG_MAX, &mm_walk_ops, w= alk); + mmap_read_unlock(mm); + } =20 - mmap_read_unlock(mm); - } + if (walk->batched) { + spin_lock_irq(&lruvec->lru_lock); + reset_batch_size(walk); + spin_unlock_irq(&lruvec->lru_lock); + } =20 - if (walk->batched) { - spin_lock_irq(&lruvec->lru_lock); - reset_batch_size(walk); - spin_unlock_irq(&lruvec->lru_lock); - } + return err; +} + +static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk) +{ + int err; =20 + walk->next_addr =3D FIRST_USER_ADDRESS; + do { + err =3D try_walk_mm(mm, walk); cond_resched(); } while (err =3D=3D -EAGAIN); } @@ -3964,6 +4022,33 @@ static bool inc_max_seq(struct lruvec *lruvec, unsig= ned long seq, int swappiness return success; } =20 +void lru_gen_scan_lruvec(struct lruvec *lruvec, unsigned long seq, + int (*accessed_cb)(pfn_t), void (*flush_cb)(void)) +{ + struct lru_gen_mm_walk *walk =3D current->reclaim_state->mm_walk; + struct mm_struct *mm =3D NULL; + + walk->lruvec =3D lruvec; + walk->seq =3D seq; + walk->accessed_cb =3D accessed_cb; + walk->swappiness =3D MAX_SWAPPINESS; + + do { + int err =3D -EBUSY; + + iterate_mm_list(walk, &mm); + if (!mm) + break; + + walk->next_addr =3D FIRST_USER_ADDRESS; + do { + err =3D try_walk_mm(mm, walk); + cond_resched(); + flush_cb(); + } while (err =3D=3D -EAGAIN); + } while (mm); 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AJvYcCVztMDLDwAmGslxm8NHfZOeoYnawwyT4CxUikc9qoLZ4wOLblo6o0FNi1g5xGRm+FJoWiIMzrmRK9nxZ2c=@vger.kernel.org X-Gm-Message-State: AOJu0YwHS9KmYXLt4rPGpmZM8w4nmdwvZMlPIuuJuyvz6v//cmSqlBKu dzG7HLTBtxNpXBUrwnOUc3gMcS2LjG3b4QLAs8qYqnGLquNr8mAmGwE3JXBZIlnaMifsma6xbO1 vsmkcVp/mCw== X-Google-Smtp-Source: AGHT+IFZ5gFWS0tV3e6VWZdQngRJrAWzxvv1iFdLvWy/bvzelevqq81SzyHG2/91MA2Kj/yFZ5fNgitHPoeVag== X-Received: from pglu36.prod.google.com ([2002:a63:1424:0:b0:af2:22fe:cfb3]) (user=kinseyho job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:2585:b0:1f5:7eb5:72c7 with SMTP id adf61e73a8af0-1fe4300f7d1mr23507348637.29.1742853793076; Mon, 24 Mar 2025 15:03:13 -0700 (PDT) Date: Mon, 24 Mar 2025 15:03:01 -0700 In-Reply-To: <20250324220301.1273038-1-kinseyho@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250324220301.1273038-1-kinseyho@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250324220301.1273038-3-kinseyho@google.com> Subject: [RFC PATCH v1 2/2] mm: klruscand: use mglru scanning for page promotion From: Kinsey Ho To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: yuanchu@google.com, AneeshKumar.KizhakeVeetil@arm.com, Hasan.Maruf@amd.com, Jonathan.Cameron@huawei.com, Michael.Day@amd.com, akpm@linux-foundation.org, dave.hansen@intel.com, david@redhat.com, feng.tang@intel.com, gourry@gourry.net, hannes@cmpxchg.org, honggyu.kim@sk.com, hughd@google.com, jhubbard@nvidia.com, k.shutemov@gmail.com, kbusch@meta.com, kmanaouil.dev@gmail.com, leesuyeon0506@gmail.com, leillc@google.com, liam.howlett@oracle.com, mgorman@techsingularity.net, mingo@redhat.com, nadav.amit@gmail.com, nphamcs@gmail.com, peterz@infradead.org, raghavendra.kt@amd.com, riel@surriel.com, rientjes@google.com, rppt@kernel.org, shivankg@amd.com, shy828301@gmail.com, sj@kernel.org, vbabka@suse.cz, weixugc@google.com, willy@infradead.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, dave@stgolabs.net, hyeonggon.yoo@sk.com, bharata@amd.com, Kinsey Ho Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Introduce a new kernel daemon, klruscand, that periodically invokes the MGLRU page table walk. It leverages the new callbacks to gather access information and forwards it to the kpromoted daemon for promotion decisions. This benefits from reusing the existing MGLRU page table walk infrastructure, which is optimized with features such as hierarchical scanning and bloom filters to reduce CPU overhead. As an additional optimization to be added in the future, we can tune the scan intervals for each memcg. Signed-off-by: Kinsey Ho Signed-off-by: Yuanchu Xie --- mm/Kconfig | 8 ++++ mm/Makefile | 1 + mm/klruscand.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 127 insertions(+) create mode 100644 mm/klruscand.c diff --git a/mm/Kconfig b/mm/Kconfig index ceaa462a0ce6..ed0fa8f2551e 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1366,6 +1366,14 @@ config KPROMOTED Promote hot pages from lower tier to top tier by using the memory access information provided by various sources. =20 +config KLRUSCAND + bool "Kernel lower tier access scan daemon" + default y + depends on KPROMOTED && LRU_GEN_WALKS_MMU + help + Scan for accesses from lower tiers by invoking MGLRU to perform + page table walks. + source "mm/damon/Kconfig" =20 endmenu diff --git a/mm/Makefile b/mm/Makefile index bf4f5f18f1f9..eb7b76db3b33 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -148,3 +148,4 @@ obj-$(CONFIG_EXECMEM) +=3D execmem.o obj-$(CONFIG_TMPFS_QUOTA) +=3D shmem_quota.o obj-$(CONFIG_PT_RECLAIM) +=3D pt_reclaim.o obj-$(CONFIG_KPROMOTED) +=3D kpromoted.o +obj-$(CONFIG_KLRUSCAND) +=3D klruscand.o diff --git a/mm/klruscand.c b/mm/klruscand.c new file mode 100644 index 000000000000..a53d43c60155 --- /dev/null +++ b/mm/klruscand.c @@ -0,0 +1,118 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +#define KLRUSCAND_INTERVAL_MS 4000 +#define BATCH_SIZE (2 << 16) + +static struct task_struct *scan_thread; +static pfn_t pfn_batch[BATCH_SIZE]; +static int batch_index; + +static void flush_cb(void) +{ + int i =3D 0; + + for (; i < batch_index; i++) { + u64 pfn =3D pfn_batch[i].val; + + kpromoted_record_access((unsigned long)pfn, NUMA_NO_NODE, + KPROMOTED_PGTABLE_SCAN, jiffies); + + if (i % 16 =3D=3D 0) + cond_resched(); + } + batch_index =3D 0; +} + +static int accessed_cb(pfn_t pfn) +{ + if (batch_index >=3D BATCH_SIZE) + return -EAGAIN; + + pfn_batch[batch_index++] =3D pfn; + return 0; +} + +static int klruscand_run(void *unused) +{ + struct lru_gen_mm_walk *walk; + + walk =3D kzalloc(sizeof(*walk), + __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN); + if (!walk) + return -ENOMEM; + + while (!kthread_should_stop()) { + unsigned long next_wake_time; + long sleep_time; + struct mem_cgroup *memcg; + int flags; + int nid; + + next_wake_time =3D jiffies + msecs_to_jiffies(KLRUSCAND_INTERVAL_MS); + + for_each_node_state(nid, N_MEMORY) { + pg_data_t *pgdat =3D NODE_DATA(nid); + struct reclaim_state rs =3D { 0 }; + + if (node_is_toptier(nid)) + continue; + + rs.mm_walk =3D walk; + set_task_reclaim_state(current, &rs); + flags =3D memalloc_noreclaim_save(); + + memcg =3D mem_cgroup_iter(NULL, NULL, NULL); + do { + struct lruvec *lruvec =3D + mem_cgroup_lruvec(memcg, pgdat); + unsigned long max_seq =3D + READ_ONCE((lruvec)->lrugen.max_seq); + + lru_gen_scan_lruvec(lruvec, max_seq, + accessed_cb, flush_cb); + cond_resched(); + } while ((memcg =3D mem_cgroup_iter(NULL, memcg, NULL))); + + memalloc_noreclaim_restore(flags); + set_task_reclaim_state(current, NULL); + memset(walk, 0, sizeof(*walk)); + } + + sleep_time =3D next_wake_time - jiffies; + if (sleep_time > 0 && sleep_time !=3D MAX_SCHEDULE_TIMEOUT) + schedule_timeout_idle(sleep_time); + } + kfree(walk); + return 0; +} + +static int __init klruscand_init(void) +{ + struct task_struct *task; + + task =3D kthread_run(klruscand_run, NULL, "klruscand"); + + if (IS_ERR(task)) { + pr_err("Failed to create klruscand kthread\n"); + return PTR_ERR(task); + } + + scan_thread =3D task; + return 0; +} +module_init(klruscand_init); --=20 2.49.0.395.g12beb8f557-goog