The patch titled
Subject: mm: multi-gen LRU: support page table walks
has been added to the -mm tree. Its filename is
mm-multi-gen-lru-support-page-table-walks.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-multi-gen-lru-support-page-table-walks.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-multi-gen-lru-support-page-table-walks.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm: multi-gen LRU: support page table walks
To further exploit spatial locality, the aging prefers to walk page tables
to search for young PTEs and promote hot pages. A kill switch will be
added in the next patch to disable this behavior. When disabled, the
aging relies on the rmap only.
NB: this behavior has nothing similar with the page table scanning in the
2.4 kernel [1], which searches page tables for old PTEs, adds cold pages
to swapcache and unmaps them.
To avoid confusion, the term "iteration" specifically means the traversal
of an entire mm_struct list; the term "walk" will be applied to page
tables and the rmap, as usual.
An mm_struct list is maintained for each memcg, and an mm_struct follows
its owner task to the new memcg when this task is migrated. Given an
lruvec, the aging iterates lruvec_memcg()->mm_list and calls
walk_page_range() with each mm_struct on this list to promote hot pages
before it increments max_seq.
When multiple page table walkers iterate the same list, each of them gets
a unique mm_struct; therefore they can run concurrently. Page table
walkers ignore any misplaced pages, e.g., if an mm_struct was migrated,
pages it left in the previous memcg will not be promoted when its current
memcg is under reclaim. Similarly, page table walkers will not promote
pages from nodes other than the one under reclaim.
This patch uses the following optimizations when walking page tables:
1. It tracks the usage of mm_struct's between context switches so that
page table walkers can skip processes that have been sleeping since
the last iteration.
2. It uses generational Bloom filters to record populated branches so
that page table walkers can reduce their search space based on the
query results, e.g., to skip page tables containing mostly holes or
misplaced pages.
3. It takes advantage of the accessed bit in non-leaf PMD entries when
CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y.
4. It does not zigzag between a PGD table and the same PMD table
spanning multiple VMAs. IOW, it finishes all the VMAs within the
range of the same PMD table before it returns to a PGD table. This
improves the cache performance for workloads that have large
numbers of tiny VMAs [2], especially when CONFIG_PGTABLE_LEVELS=5.
Server benchmark results:
Single workload:
fio (buffered I/O): no change
Single workload:
memcached (anon): +[8, 10]%
Ops/sec KB/sec
patch1-7: 1193918.93 46438.15
patch1-8: 1301954.44 50640.27
Configurations:
no change
Client benchmark results:
kswapd profiles:
patch1-7
45.90% lzo1x_1_do_compress (real work)
9.14% page_vma_mapped_walk
6.81% _raw_spin_unlock_irq
2.80% ptep_clear_flush
2.34% __zram_bvec_write
2.29% do_raw_spin_lock
1.84% lru_gen_look_around
1.78% memmove
1.74% obj_malloc
1.50% free_unref_page_list
patch1-8
46.96% lzo1x_1_do_compress (real work)
7.55% page_vma_mapped_walk
5.89% _raw_spin_unlock_irq
3.33% walk_pte_range
2.65% ptep_clear_flush
2.23% __zram_bvec_write
2.08% do_raw_spin_lock
1.83% memmove
1.65% obj_malloc
1.47% free_unref_page_list
Configurations:
no change
[1] https://lwn.net/Articles/23732/
[2] https://source.android.com/devices/tech/debug/scudo
Link: https://lkml.kernel.org/r/20220407031525.2368067-9-yuzhao@xxxxxxxxxx
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Acked-by: Brian Geffon <bgeffon@xxxxxxxxxx>
Acked-by: Jan Alexander Steffens (heftig) <heftig@xxxxxxxxxxxxx>
Acked-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Acked-by: Steven Barrett <steven@xxxxxxxxxxxx>
Acked-by: Suleiman Souhlal <suleiman@xxxxxxxxxx>
Tested-by: Daniel Byrne <djbyrne@xxxxxxx>
Tested-by: Donald Carr <d@xxxxxxxxxxxxxxx>
Tested-by: Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx>
Tested-by: Konstantin Kharlamov <Hi-Angel@xxxxxxxxx>
Tested-by: Shuang Zhai <szhai2@xxxxxxxxxxxxxxxx>
Tested-by: Sofia Trinh <sofia.trinh@edi.works>
Tested-by: Vaibhav Jain <vaibhav@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/fs/exec.c~mm-multi-gen-lru-support-page-table-walks
+++ a/fs/exec.c
@@ -1015,6 +1015,7 @@ static int exec_mmap(struct mm_struct *m
active_mm = tsk->active_mm;
tsk->active_mm = mm;
tsk->mm = mm;
+ lru_gen_add_mm(mm);
/*
* This prevents preemption while active_mm is being loaded and
* it and mm are being updated, which could cause problems for
@@ -1027,6 +1028,7 @@ static int exec_mmap(struct mm_struct *m
activate_mm(active_mm, mm);
if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
local_irq_enable();
+ lru_gen_use_mm(mm);
tsk->mm->vmacache_seqnum = 0;
vmacache_flush(tsk);
task_unlock(tsk);
--- a/include/linux/memcontrol.h~mm-multi-gen-lru-support-page-table-walks
+++ a/include/linux/memcontrol.h
@@ -344,6 +344,11 @@ struct mem_cgroup {
struct deferred_split deferred_split_queue;
#endif
+#ifdef CONFIG_LRU_GEN
+ /* per-memcg mm_struct list */
+ struct lru_gen_mm_list mm_list;
+#endif
+
struct mem_cgroup_per_node *nodeinfo[];
};
--- a/include/linux/mm_types.h~mm-multi-gen-lru-support-page-table-walks
+++ a/include/linux/mm_types.h
@@ -3,6 +3,7 @@
#define _LINUX_MM_TYPES_H
#include <linux/mm_types_task.h>
+#include <linux/sched.h>
#include <linux/auxvec.h>
#include <linux/kref.h>
@@ -17,6 +18,8 @@
#include <linux/page-flags-layout.h>
#include <linux/workqueue.h>
#include <linux/seqlock.h>
+#include <linux/nodemask.h>
+#include <linux/mmdebug.h>
#include <asm/mmu.h>
@@ -649,6 +652,22 @@ struct mm_struct {
#ifdef CONFIG_IOMMU_SVA
u32 pasid;
#endif
+#ifdef CONFIG_LRU_GEN
+ struct {
+ /* this mm_struct is on lru_gen_mm_list */
+ struct list_head list;
+#ifdef CONFIG_MEMCG
+ /* points to the memcg of "owner" above */
+ struct mem_cgroup *memcg;
+#endif
+ /*
+ * Set when switching to this mm_struct, as a hint of
+ * whether it has been used since the last time per-node
+ * page table walkers cleared the corresponding bits.
+ */
+ nodemask_t nodes;
+ } lru_gen;
+#endif /* CONFIG_LRU_GEN */
} __randomize_layout;
/*
@@ -675,6 +694,65 @@ static inline cpumask_t *mm_cpumask(stru
return (struct cpumask *)&mm->cpu_bitmap;
}
+#ifdef CONFIG_LRU_GEN
+
+struct lru_gen_mm_list {
+ /* mm_struct list for page table walkers */
+ struct list_head fifo;
+ /* protects the list above */
+ spinlock_t lock;
+};
+
+void lru_gen_add_mm(struct mm_struct *mm);
+void lru_gen_del_mm(struct mm_struct *mm);
+#ifdef CONFIG_MEMCG
+void lru_gen_migrate_mm(struct mm_struct *mm);
+#endif
+
+static inline void lru_gen_init_mm(struct mm_struct *mm)
+{
+ INIT_LIST_HEAD(&mm->lru_gen.list);
+#ifdef CONFIG_MEMCG
+ mm->lru_gen.memcg = NULL;
+#endif
+ nodes_clear(mm->lru_gen.nodes);
+}
+
+static inline void lru_gen_use_mm(struct mm_struct *mm)
+{
+ /* unlikely but not a bug when racing with lru_gen_migrate_mm() */
+ VM_WARN_ON(list_empty(&mm->lru_gen.list));
+
+ if (!(current->flags & PF_KTHREAD) && !nodes_full(mm->lru_gen.nodes))
+ nodes_setall(mm->lru_gen.nodes);
+}
+
+#else /* !CONFIG_LRU_GEN */
+
+static inline void lru_gen_add_mm(struct mm_struct *mm)
+{
+}
+
+static inline void lru_gen_del_mm(struct mm_struct *mm)
+{
+}
+
+#ifdef CONFIG_MEMCG
+static inline void lru_gen_migrate_mm(struct mm_struct *mm)
+{
+}
+#endif
+
+static inline void lru_gen_init_mm(struct mm_struct *mm)
+{
+}
+
+static inline void lru_gen_use_mm(struct mm_struct *mm)
+{
+}
+
+#endif /* CONFIG_LRU_GEN */
+
struct mmu_gather;
extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
--- a/include/linux/mmzone.h~mm-multi-gen-lru-support-page-table-walks
+++ a/include/linux/mmzone.h
@@ -424,6 +424,58 @@ struct lru_gen_struct {
atomic_long_t refaulted[NR_HIST_GENS][ANON_AND_FILE][MAX_NR_TIERS];
};
+enum {
+ MM_PTE_TOTAL, /* total leaf entries */
+ MM_PTE_OLD, /* old leaf entries */
+ MM_PTE_YOUNG, /* young leaf entries */
+ MM_PMD_TOTAL, /* total non-leaf entries */
+ MM_PMD_FOUND, /* non-leaf entries found in Bloom filters */
+ MM_PMD_ADDED, /* non-leaf entries added to Bloom filters */
+ NR_MM_STATS
+};
+
+/* mnemonic codes for the mm stats above */
+#define MM_STAT_CODES "toydfa"
+
+/* double-buffering Bloom filters */
+#define NR_BLOOM_FILTERS 2
+
+struct lru_gen_mm_state {
+ /* set to max_seq after each iteration */
+ unsigned long seq;
+ /* where the current iteration starts (inclusive) */
+ struct list_head *head;
+ /* where the last iteration ends (exclusive) */
+ struct list_head *tail;
+ /* to wait for the last page table walker to finish */
+ struct wait_queue_head wait;
+ /* Bloom filters flip after each iteration */
+ unsigned long *filters[NR_BLOOM_FILTERS];
+ /* the mm stats for debugging */
+ unsigned long stats[NR_HIST_GENS][NR_MM_STATS];
+ /* the number of concurrent page table walkers */
+ int nr_walkers;
+};
+
+struct lru_gen_mm_walk {
+ /* the lruvec under reclaim */
+ struct lruvec *lruvec;
+ /* unstable max_seq from lru_gen_struct */
+ unsigned long max_seq;
+ /* the next address within an mm to scan */
+ unsigned long next_addr;
+ /* to batch page table entries */
+ unsigned long bitmap[BITS_TO_LONGS(MIN_LRU_BATCH)];
+ /* to batch promoted pages */
+ int nr_pages[MAX_NR_GENS][ANON_AND_FILE][MAX_NR_ZONES];
+ /* to batch the mm stats */
+ int mm_stats[NR_MM_STATS];
+ /* total batched items */
+ int batched;
+ bool can_swap;
+ bool full_scan;
+};
+
void lru_gen_init_lruvec(struct lruvec *lruvec);
void lru_gen_look_around(struct page_vma_mapped_walk *pvmw);
@@ -474,6 +526,8 @@ struct lruvec {
#ifdef CONFIG_LRU_GEN
/* evictable pages divided into generations */
struct lru_gen_struct lrugen;
+ /* to concurrently iterate lru_gen_mm_list */
+ struct lru_gen_mm_state mm_state;
#endif
#ifdef CONFIG_MEMCG
struct pglist_data *pgdat;
@@ -1067,6 +1121,11 @@ typedef struct pglist_data {
unsigned long flags;
+#ifdef CONFIG_LRU_GEN
+ /* kswap mm walk data */
+ struct lru_gen_mm_walk mm_walk;
+#endif
+
ZONE_PADDING(_pad2_)
/* Per-node vmstats */
--- a/include/linux/swap.h~mm-multi-gen-lru-support-page-table-walks
+++ a/include/linux/swap.h
@@ -157,6 +157,10 @@ union swap_header {
*/
struct reclaim_state {
unsigned long reclaimed_slab;
+#ifdef CONFIG_LRU_GEN
+ /* per-thread mm walk data */
+ struct lru_gen_mm_walk *mm_walk;
+#endif
};
#ifdef __KERNEL__
--- a/kernel/exit.c~mm-multi-gen-lru-support-page-table-walks
+++ a/kernel/exit.c
@@ -466,6 +466,7 @@ assign_new_owner:
goto retry;
}
WRITE_ONCE(mm->owner, c);
+ lru_gen_migrate_mm(mm);
task_unlock(c);
put_task_struct(c);
}
--- a/kernel/fork.c~mm-multi-gen-lru-support-page-table-walks
+++ a/kernel/fork.c
@@ -1146,6 +1146,7 @@ static struct mm_struct *mm_init(struct
goto fail_nocontext;
mm->user_ns = get_user_ns(user_ns);
+ lru_gen_init_mm(mm);
return mm;
fail_nocontext:
@@ -1189,6 +1190,7 @@ static inline void __mmput(struct mm_str
if (mm->binfmt)
module_put(mm->binfmt->module);
mm_pasid_drop(mm);
+ lru_gen_del_mm(mm);
mmdrop(mm);
}
@@ -2658,6 +2660,13 @@ pid_t kernel_clone(struct kernel_clone_a
get_task_struct(p);
}
+ if (IS_ENABLED(CONFIG_LRU_GEN) && !(clone_flags & CLONE_VM)) {
+ /* lock the task to synchronize with memcg migration */
+ task_lock(p);
+ lru_gen_add_mm(p->mm);
+ task_unlock(p);
+ }
+
wake_up_new_task(p);
/* forking complete and child started to run, tell ptracer */
--- a/kernel/sched/core.c~mm-multi-gen-lru-support-page-table-walks
+++ a/kernel/sched/core.c
@@ -5057,6 +5057,7 @@ context_switch(struct rq *rq, struct tas
* finish_task_switch()'s mmdrop().
*/
switch_mm_irqs_off(prev->active_mm, next->mm, next);
+ lru_gen_use_mm(next->mm);
if (!prev->mm) { // from kernel
/* will mmdrop() in finish_task_switch(). */
--- a/mm/memcontrol.c~mm-multi-gen-lru-support-page-table-walks
+++ a/mm/memcontrol.c
@@ -6092,6 +6092,29 @@ static void mem_cgroup_move_task(void)
}
#endif
+#ifdef CONFIG_LRU_GEN
+static void mem_cgroup_attach(struct cgroup_taskset *tset)
+{
+ struct cgroup_subsys_state *css;
+ struct task_struct *task = NULL;
+
+ cgroup_taskset_for_each_leader(task, css, tset)
+ break;
+
+ if (!task)
+ return;
+
+ task_lock(task);
+ if (task->mm && task->mm->owner == task)
+ lru_gen_migrate_mm(task->mm);
+ task_unlock(task);
+}
+#else
+static void mem_cgroup_attach(struct cgroup_taskset *tset)
+{
+}
+#endif /* CONFIG_LRU_GEN */
+
static int seq_puts_memcg_tunable(struct seq_file *m, unsigned long value)
{
if (value == PAGE_COUNTER_MAX)
@@ -6437,6 +6460,7 @@ struct cgroup_subsys memory_cgrp_subsys
.css_reset = mem_cgroup_css_reset,
.css_rstat_flush = mem_cgroup_css_rstat_flush,
.can_attach = mem_cgroup_can_attach,
+ .attach = mem_cgroup_attach,
.cancel_attach = mem_cgroup_cancel_attach,
.post_attach = mem_cgroup_move_task,
.dfl_cftypes = memory_files,
--- a/mm/vmscan.c~mm-multi-gen-lru-support-page-table-walks
+++ a/mm/vmscan.c
@@ -50,6 +50,8 @@
#include <linux/printk.h>
#include <linux/dax.h>
#include <linux/psi.h>
+#include <linux/pagewalk.h>
+#include <linux/shmem_fs.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -3031,7 +3033,7 @@ static int folio_lru_tier(struct folio *
return lru_tier_from_refs(refs);
}
-static struct lruvec __maybe_unused *get_lruvec(struct mem_cgroup *memcg, int nid)
+static struct lruvec *get_lruvec(struct mem_cgroup *memcg, int nid)
{
struct pglist_data *pgdat = NODE_DATA(nid);
@@ -3077,6 +3079,374 @@ static bool __maybe_unused seq_is_valid(
}
/******************************************************************************
+ * mm_struct list
+ ******************************************************************************/
+
+static struct lru_gen_mm_list *get_mm_list(struct mem_cgroup *memcg)
+{
+ static struct lru_gen_mm_list mm_list = {
+ .fifo = LIST_HEAD_INIT(mm_list.fifo),
+ .lock = __SPIN_LOCK_UNLOCKED(mm_list.lock),
+ };
+
+#ifdef CONFIG_MEMCG
+ if (memcg)
+ return &memcg->mm_list;
+#endif
+ VM_BUG_ON(!mem_cgroup_disabled());
+
+ return &mm_list;
+}
+
+void lru_gen_add_mm(struct mm_struct *mm)
+{
+ int nid;
+ struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+
+ VM_BUG_ON_MM(!list_empty(&mm->lru_gen.list), mm);
+#ifdef CONFIG_MEMCG
+ VM_BUG_ON_MM(mm->lru_gen.memcg, mm);
+ mm->lru_gen.memcg = memcg;
+#endif
+ spin_lock(&mm_list->lock);
+
+ for_each_node_state(nid, N_MEMORY) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ if (!lruvec)
+ continue;
+
+ if (lruvec->mm_state.tail == &mm_list->fifo)
+ lruvec->mm_state.tail = &mm->lru_gen.list;
+ }
+
+ list_add_tail(&mm->lru_gen.list, &mm_list->fifo);
+
+ spin_unlock(&mm_list->lock);
+}
+
+void lru_gen_del_mm(struct mm_struct *mm)
+{
+ int nid;
+ struct lru_gen_mm_list *mm_list;
+ struct mem_cgroup *memcg = NULL;
+
+ if (list_empty(&mm->lru_gen.list))
+ return;
+
+#ifdef CONFIG_MEMCG
+ memcg = mm->lru_gen.memcg;
+#endif
+ mm_list = get_mm_list(memcg);
+
+ spin_lock(&mm_list->lock);
+
+ for_each_node(nid) {
+ struct lruvec *lruvec = get_lruvec(memcg, nid);
+
+ if (!lruvec)
+ continue;
+
+ if (lruvec->mm_state.tail == &mm->lru_gen.list)
+ lruvec->mm_state.tail = lruvec->mm_state.tail->next;
+
+ if (lruvec->mm_state.head != &mm->lru_gen.list)
+ continue;
+
+ lruvec->mm_state.head = lruvec->mm_state.head->next;
+ if (lruvec->mm_state.head == &mm_list->fifo)
+ WRITE_ONCE(lruvec->mm_state.seq, lruvec->mm_state.seq + 1);
+ }
+
+ list_del_init(&mm->lru_gen.list);
+
+ spin_unlock(&mm_list->lock);
+
+#ifdef CONFIG_MEMCG
+ mem_cgroup_put(mm->lru_gen.memcg);
+ mm->lru_gen.memcg = NULL;
+#endif
+}
+
+#ifdef CONFIG_MEMCG
+void lru_gen_migrate_mm(struct mm_struct *mm)
+{
+ struct mem_cgroup *memcg;
+
+ lockdep_assert_held(&mm->owner->alloc_lock);
+
+ /* for mm_update_next_owner() */
+ if (mem_cgroup_disabled())
+ return;
+
+ rcu_read_lock();
+ memcg = mem_cgroup_from_task(mm->owner);
+ rcu_read_unlock();
+ if (memcg == mm->lru_gen.memcg)
+ return;
+
+ VM_BUG_ON_MM(!mm->lru_gen.memcg, mm);
+ VM_BUG_ON_MM(list_empty(&mm->lru_gen.list), mm);
+
+ lru_gen_del_mm(mm);
+ lru_gen_add_mm(mm);
+}
+#endif
+
+/*
+ * Bloom filters with m=1<<15, k=2 and the false positive rates of ~1/5 when
+ * n=10,000 and ~1/2 when n=20,000, where, conventionally, m is the number of
+ * bits in a bitmap, k is the number of hash functions and n is the number of
+ * inserted items.
+ *
+ * Page table walkers use one of the two filters to reduce their search space.
+ * To get rid of non-leaf entries that no longer have enough leaf entries, the
+ * aging uses the double-buffering technique to flip to the other filter each
+ * time it produces a new generation. For non-leaf entries that have enough
+ * leaf entries, the aging carries them over to the next generation in
+ * walk_pmd_range(); the eviction also report them when walking the rmap
+ * in lru_gen_look_around().
+ *
+ * For future optimizations:
+ * 1. It's not necessary to keep both filters all the time. The spare one can be
+ * freed after the RCU grace period and reallocated if needed again.
+ * 2. And when reallocating, it's worth scaling its size according to the number
+ * of inserted entries in the other filter, to reduce the memory overhead on
+ * small systems and false positives on large systems.
+ * 3. Jenkins' hash function is an alternative to Knuth's.
+ */
+#define BLOOM_FILTER_SHIFT 15
+
+static inline int filter_gen_from_seq(unsigned long seq)
+{
+ return seq % NR_BLOOM_FILTERS;
+}
+
+static void get_item_key(void *item, int *key)
+{
+ u32 hash = hash_ptr(item, BLOOM_FILTER_SHIFT * 2);
+
+ BUILD_BUG_ON(BLOOM_FILTER_SHIFT * 2 > BITS_PER_TYPE(u32));
+
+ key[0] = hash & (BIT(BLOOM_FILTER_SHIFT) - 1);
+ key[1] = hash >> BLOOM_FILTER_SHIFT;
+}
+
+static void reset_bloom_filter(struct lruvec *lruvec, unsigned long seq)
+{
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
+
+ filter = lruvec->mm_state.filters[gen];
+ if (filter) {
+ bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
+ return;
+ }
+
+ filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT), GFP_ATOMIC);
+ WRITE_ONCE(lruvec->mm_state.filters[gen], filter);
+}
+
+static void update_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
+{
+ int key[2];
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ filter = READ_ONCE(lruvec->mm_state.filters[gen]);
+ if (!filter)
+ return;
+
+ get_item_key(item, key);
+
+ if (!test_bit(key[0], filter))
+ set_bit(key[0], filter);
+ if (!test_bit(key[1], filter))
+ set_bit(key[1], filter);
+}
+
+static bool test_bloom_filter(struct lruvec *lruvec, unsigned long seq, void *item)
+{
+ int key[2];
+ unsigned long *filter;
+ int gen = filter_gen_from_seq(seq);
+
+ filter = READ_ONCE(lruvec->mm_state.filters[gen]);
+ if (!filter)
+ return true;
+
+ get_item_key(item, key);
+
+ return test_bit(key[0], filter) && test_bit(key[1], filter);
+}
+
+static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
+{
+ int i;
+ int hist;
+
+ lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
+
+ if (walk) {
+ hist = lru_hist_from_seq(walk->max_seq);
+
+ for (i = 0; i < NR_MM_STATS; i++) {
+ WRITE_ONCE(lruvec->mm_state.stats[hist][i],
+ lruvec->mm_state.stats[hist][i] + walk->mm_stats[i]);
+ walk->mm_stats[i] = 0;
+ }
+ }
+
+ if (NR_HIST_GENS > 1 && last) {
+ hist = lru_hist_from_seq(lruvec->mm_state.seq + 1);
+
+ for (i = 0; i < NR_MM_STATS; i++)
+ WRITE_ONCE(lruvec->mm_state.stats[hist][i], 0);
+ }
+}
+
+static bool should_skip_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
+{
+ int type;
+ unsigned long size = 0;
+ struct pglist_data *pgdat = lruvec_pgdat(walk->lruvec);
+
+ if (!walk->full_scan && cpumask_empty(mm_cpumask(mm)) &&
+ !node_isset(pgdat->node_id, mm->lru_gen.nodes))
+ return true;
+
+ node_clear(pgdat->node_id, mm->lru_gen.nodes);
+
+ for (type = !walk->can_swap; type < ANON_AND_FILE; type++) {
+ size += type ? get_mm_counter(mm, MM_FILEPAGES) :
+ get_mm_counter(mm, MM_ANONPAGES) +
+ get_mm_counter(mm, MM_SHMEMPAGES);
+ }
+
+ if (size < MIN_LRU_BATCH)
+ return true;
+
+ if (mm_is_oom_victim(mm))
+ return true;
+
+ return !mmget_not_zero(mm);
+}
+
+static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
+ struct mm_struct **iter)
+{
+ bool first = false;
+ bool last = true;
+ struct mm_struct *mm = NULL;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+ struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
+
+ /*
+ * There are four interesting cases for this page table walker:
+ * 1. It tries to start a new iteration of mm_list with a stale max_seq;
+ * there is nothing to be done.
+ * 2. It's the first of the current generation, and it needs to reset
+ * the Bloom filter for the next generation.
+ * 3. It reaches the end of mm_list, and it needs to increment
+ * mm_state->seq; the iteration is done.
+ * 4. It's the last of the current generation, and it needs to reset the
+ * mm stats counters for the next generation.
+ */
+ if (*iter)
+ mmput_async(*iter);
+ else if (walk->max_seq <= READ_ONCE(mm_state->seq))
+ return false;
+
+ spin_lock(&mm_list->lock);
+
+ VM_BUG_ON(mm_state->seq + 1 < walk->max_seq);
+ VM_BUG_ON(*iter && mm_state->seq > walk->max_seq);
+ VM_BUG_ON(*iter && !mm_state->nr_walkers);
+
+ if (walk->max_seq <= mm_state->seq) {
+ if (!*iter)
+ last = false;
+ goto done;
+ }
+
+ if (!mm_state->nr_walkers) {
+ VM_BUG_ON(mm_state->head && mm_state->head != &mm_list->fifo);
+
+ mm_state->head = mm_list->fifo.next;
+ first = true;
+ }
+
+ while (!mm && mm_state->head != &mm_list->fifo) {
+ mm = list_entry(mm_state->head, struct mm_struct, lru_gen.list);
+
+ mm_state->head = mm_state->head->next;
+
+ /* full scan for those added after the last iteration */
+ if (!mm_state->tail || mm_state->tail == &mm->lru_gen.list) {
+ mm_state->tail = mm_state->head;
+ walk->full_scan = true;
+ }
+
+ if (should_skip_mm(mm, walk))
+ mm = NULL;
+ }
+
+ if (mm_state->head == &mm_list->fifo)
+ WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
+done:
+ if (*iter && !mm)
+ mm_state->nr_walkers--;
+ if (!*iter && mm)
+ mm_state->nr_walkers++;
+
+ if (mm_state->nr_walkers)
+ last = false;
+
+ if (mm && first)
+ reset_bloom_filter(lruvec, walk->max_seq + 1);
+
+ if (*iter || last)
+ reset_mm_stats(lruvec, walk, last);
+
+ spin_unlock(&mm_list->lock);
+
+ *iter = mm;
+
+ return last;
+}
+
+static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
+{
+ bool success = false;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+ struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
+ struct lru_gen_mm_state *mm_state = &lruvec->mm_state;
+
+ if (max_seq <= READ_ONCE(mm_state->seq))
+ return false;
+
+ spin_lock(&mm_list->lock);
+
+ VM_BUG_ON(mm_state->seq + 1 < max_seq);
+
+ if (max_seq > mm_state->seq && !mm_state->nr_walkers) {
+ VM_BUG_ON(mm_state->head && mm_state->head != &mm_list->fifo);
+
+ WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
+ reset_mm_stats(lruvec, NULL, true);
+ success = true;
+ }
+
+ spin_unlock(&mm_list->lock);
+
+ return success;
+}
+
+/******************************************************************************
* refault feedback loop
******************************************************************************/
@@ -3229,6 +3599,476 @@ static int folio_inc_gen(struct lruvec *
return new_gen;
}
+static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
+ int old_gen, int new_gen)
+{
+ int type = folio_is_file_lru(folio);
+ int zone = folio_zonenum(folio);
+ int delta = folio_nr_pages(folio);
+
+ VM_BUG_ON(old_gen >= MAX_NR_GENS);
+ VM_BUG_ON(new_gen >= MAX_NR_GENS);
+
+ walk->batched++;
+
+ walk->nr_pages[old_gen][type][zone] -= delta;
+ walk->nr_pages[new_gen][type][zone] += delta;
+}
+
+static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
+{
+ int gen, type, zone;
+ struct lru_gen_struct *lrugen = &lruvec->lrugen;
+
+ walk->batched = 0;
+
+ for_each_gen_type_zone(gen, type, zone) {
+ enum lru_list lru = type * LRU_INACTIVE_FILE;
+ int delta = walk->nr_pages[gen][type][zone];
+
+ if (!delta)
+ continue;
+
+ walk->nr_pages[gen][type][zone] = 0;
+ WRITE_ONCE(lrugen->nr_pages[gen][type][zone],
+ lrugen->nr_pages[gen][type][zone] + delta);
+
+ if (lru_gen_is_active(lruvec, gen))
+ lru += LRU_ACTIVE;
+ __update_lru_size(lruvec, lru, zone, delta);
+ }
+}
+
+static int should_skip_vma(unsigned long start, unsigned long end, struct mm_walk *walk)
+{
+ struct address_space *mapping;
+ struct vm_area_struct *vma = walk->vma;
+ struct lru_gen_mm_walk *priv = walk->private;
+
+ if (!vma_is_accessible(vma) || is_vm_hugetlb_page(vma) ||
+ (vma->vm_flags & (VM_LOCKED | VM_SPECIAL | VM_SEQ_READ | VM_RAND_READ)) ||
+ vma == get_gate_vma(vma->vm_mm))
+ return true;
+
+ if (vma_is_anonymous(vma))
+ return !priv->can_swap;
+
+ if (WARN_ON_ONCE(!vma->vm_file || !vma->vm_file->f_mapping))
+ return true;
+
+ mapping = vma->vm_file->f_mapping;
+ if (mapping_unevictable(mapping))
+ return true;
+
+ /* check readpage to exclude special mappings like dax, etc. */
+ return shmem_mapping(mapping) ? !priv->can_swap : !mapping->a_ops->readpage;
+}
+
+/*
+ * Some userspace memory allocators map many single-page VMAs. Instead of
+ * returning back to the PGD table for each of such VMAs, finish an entire PMD
+ * table to reduce zigzags and improve cache performance.
+ */
+static bool get_next_vma(struct mm_walk *walk, unsigned long mask, unsigned long size,
+ unsigned long *start, unsigned long *end)
+{
+ unsigned long next = round_up(*end, size);
+
+ VM_BUG_ON(mask & size);
+ VM_BUG_ON(*start >= *end);
+ VM_BUG_ON((next & mask) != (*start & mask));
+
+ while (walk->vma) {
+ if (next >= walk->vma->vm_end) {
+ walk->vma = walk->vma->vm_next;
+ continue;
+ }
+
+ if ((next & mask) != (walk->vma->vm_start & mask))
+ return false;
+
+ if (should_skip_vma(walk->vma->vm_start, walk->vma->vm_end, walk)) {
+ walk->vma = walk->vma->vm_next;
+ continue;
+ }
+
+ *start = max(next, walk->vma->vm_start);
+ next = (next | ~mask) + 1;
+ /* rounded-up boundaries can wrap to 0 */
+ *end = next && next < walk->vma->vm_end ? next : walk->vma->vm_end;
+
+ return true;
+ }
+
+ return false;
+}
+
+static bool suitable_to_scan(int total, int young)
+{
+ int n = clamp_t(int, cache_line_size() / sizeof(pte_t), 2, 8);
+
+ /* suitable if the average number of young PTEs per cacheline is >=1 */
+ return young * n >= total;
+}
+
+static bool walk_pte_range(pmd_t *pmd, unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ int i;
+ pte_t *pte;
+ spinlock_t *ptl;
+ unsigned long addr;
+ int total = 0;
+ int young = 0;
+ struct lru_gen_mm_walk *priv = walk->private;
+ struct mem_cgroup *memcg = lruvec_memcg(priv->lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec);
+ int old_gen, new_gen = lru_gen_from_seq(priv->max_seq);
+
+ VM_BUG_ON(pmd_leaf(*pmd));
+
+ ptl = pte_lockptr(walk->mm, pmd);
+ if (!spin_trylock(ptl))
+ return false;
+
+ arch_enter_lazy_mmu_mode();
+
+ pte = pte_offset_map(pmd, start & PMD_MASK);
+restart:
+ for (i = pte_index(start), addr = start; addr != end; i++, addr += PAGE_SIZE) {
+ struct folio *folio;
+ unsigned long pfn = pte_pfn(pte[i]);
+
+ VM_BUG_ON(addr < walk->vma->vm_start || addr >= walk->vma->vm_end);
+
+ total++;
+ priv->mm_stats[MM_PTE_TOTAL]++;
+
+ if (!pte_present(pte[i]) || is_zero_pfn(pfn))
+ continue;
+
+ if (WARN_ON_ONCE(pte_devmap(pte[i]) || pte_special(pte[i])))
+ continue;
+
+ if (!pte_young(pte[i])) {
+ priv->mm_stats[MM_PTE_OLD]++;
+ continue;
+ }
+
+ VM_BUG_ON(!pfn_valid(pfn));
+ if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
+ continue;
+
+ folio = pfn_folio(pfn);
+ if (folio_nid(folio) != pgdat->node_id)
+ continue;
+
+ if (folio_memcg_rcu(folio) != memcg)
+ continue;
+
+ if (!ptep_test_and_clear_young(walk->vma, addr, pte + i))
+ continue;
+
+ young++;
+ priv->mm_stats[MM_PTE_YOUNG]++;
+
+ if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
+ !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_test_swapcache(folio)))
+ folio_mark_dirty(folio);
+
+ old_gen = folio_update_gen(folio, new_gen);
+ if (old_gen >= 0 && old_gen != new_gen)
+ update_batch_size(priv, folio, old_gen, new_gen);
+ }
+
+ if (i < PTRS_PER_PTE && get_next_vma(walk, PMD_MASK, PAGE_SIZE, &start, &end))
+ goto restart;
+
+ pte_unmap(pte);
+
+ arch_leave_lazy_mmu_mode();
+ spin_unlock(ptl);
+
+ return suitable_to_scan(total, young);
+}
+
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG)
+static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
+ struct mm_walk *walk, unsigned long *start)
+{
+ int i;
+ pmd_t *pmd;
+ spinlock_t *ptl;
+ struct lru_gen_mm_walk *priv = walk->private;
+ struct mem_cgroup *memcg = lruvec_memcg(priv->lruvec);
+ struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec);
+ int old_gen, new_gen = lru_gen_from_seq(priv->max_seq);
+
+ VM_BUG_ON(pud_leaf(*pud));
+
+ /* try to batch at most 1+MIN_LRU_BATCH+1 entries */
+ if (*start == -1) {
+ *start = next;
+ return;
+ }
+
+ i = next == -1 ? 0 : pmd_index(next) - pmd_index(*start);
+ if (i && i <= MIN_LRU_BATCH) {
+ __set_bit(i - 1, priv->bitmap);
+ return;
+ }
+
+ pmd = pmd_offset(pud, *start);
+
+ ptl = pmd_lockptr(walk->mm, pmd);
+ if (!spin_trylock(ptl))
+ goto done;
+
+ arch_enter_lazy_mmu_mode();
+
+ do {
+ struct folio *folio;
+ unsigned long pfn = pmd_pfn(pmd[i]);
+ unsigned long addr = i ? (*start & PMD_MASK) + i * PMD_SIZE : *start;
+
+ VM_BUG_ON(addr < vma->vm_start || addr >= vma->vm_end);
+
+ if (!pmd_present(pmd[i]) || is_huge_zero_pmd(pmd[i]))
+ goto next;
+
+ if (WARN_ON_ONCE(pmd_devmap(pmd[i])))
+ goto next;
+
+ if (!pmd_trans_huge(pmd[i])) {
+ if (IS_ENABLED(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG))
+ pmdp_test_and_clear_young(vma, addr, pmd + i);
+ goto next;
+ }
+
+ VM_BUG_ON(!pfn_valid(pfn));
+ if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
+ goto next;
+
+ folio = pfn_folio(pfn);
+ if (folio_nid(folio) != pgdat->node_id)
+ goto next;
+
+ if (folio_memcg_rcu(folio) != memcg)
+ goto next;
+
+ if (!pmdp_test_and_clear_young(vma, addr, pmd + i))
+ goto next;
+
+ priv->mm_stats[MM_PTE_YOUNG]++;
+
+ if (pmd_dirty(pmd[i]) && !folio_test_dirty(folio) &&
+ !(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
+ !folio_test_swapcache(folio)))
+ folio_mark_dirty(folio);
+
+ old_gen = folio_update_gen(folio, new_gen);
+ if (old_gen >= 0 && old_gen != new_gen)
+ update_batch_size(priv, folio, old_gen, new_gen);
+next:
+ i = i > MIN_LRU_BATCH ? 0 :
+ find_next_bit(priv->bitmap, MIN_LRU_BATCH, i) + 1;
+ } while (i <= MIN_LRU_BATCH);
+
+ arch_leave_lazy_mmu_mode();
+ spin_unlock(ptl);
+done:
+ *start = -1;
+ bitmap_zero(priv->bitmap, MIN_LRU_BATCH);
+}
+#else
+static void walk_pmd_range_locked(pud_t *pud, unsigned long next, struct vm_area_struct *vma,
+ struct mm_walk *walk, unsigned long *start)
+{
+}
+#endif
+
+static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ int i;
+ pmd_t *pmd;
+ unsigned long next;
+ unsigned long addr;
+ struct vm_area_struct *vma;
+ unsigned long pos = -1;
+ struct lru_gen_mm_walk *priv = walk->private;
+
+ VM_BUG_ON(pud_leaf(*pud));
+
+ /*
+ * Finish an entire PMD in two passes: the first only reaches to PTE
+ * tables to avoid taking the PMD lock; the second, if necessary, takes
+ * the PMD lock to clear the accessed bit in PMD entries.
+ */
+ pmd = pmd_offset(pud, start & PUD_MASK);
+restart:
+ /* walk_pte_range() may call get_next_vma() */
+ vma = walk->vma;
+ for (i = pmd_index(start), addr = start; addr != end; i++, addr = next) {
+ pmd_t val = pmd_read_atomic(pmd + i);
+
+ /* for pmd_read_atomic() */
+ barrier();
+
+ next = pmd_addr_end(addr, end);
+
+ if (!pmd_present(val)) {
+ priv->mm_stats[MM_PTE_TOTAL]++;
+ continue;
+ }
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ if (pmd_trans_huge(val)) {
+ unsigned long pfn = pmd_pfn(val);
+ struct pglist_data *pgdat = lruvec_pgdat(priv->lruvec);
+
+ priv->mm_stats[MM_PTE_TOTAL]++;
+
+ if (is_huge_zero_pmd(val))
+ continue;
+
+ if (!pmd_young(val)) {
+ priv->mm_stats[MM_PTE_OLD]++;
+ continue;
+ }
+
+ if (pfn < pgdat->node_start_pfn || pfn >= pgdat_end_pfn(pgdat))
+ continue;
+
+ walk_pmd_range_locked(pud, addr, vma, walk, &pos);
+ continue;
+ }
+#endif
+ priv->mm_stats[MM_PMD_TOTAL]++;
+
+#ifdef CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG
+ if (!pmd_young(val))
+ continue;
+
+ walk_pmd_range_locked(pud, addr, vma, walk, &pos);
+#endif
+ if (!priv->full_scan && !test_bloom_filter(priv->lruvec, priv->max_seq, pmd + i))
+ continue;
+
+ priv->mm_stats[MM_PMD_FOUND]++;
+
+ if (!walk_pte_range(&val, addr, next, walk))
+ continue;
+
+ priv->mm_stats[MM_PMD_ADDED]++;
+
+ /* carry over to the next generation */
+ update_bloom_filter(priv->lruvec, priv->max_seq + 1, pmd + i);
+ }
+
+ walk_pmd_range_locked(pud, -1, vma, walk, &pos);
+
+ if (i < PTRS_PER_PMD && get_next_vma(walk, PUD_MASK, PMD_SIZE, &start, &end))
+ goto restart;
+}
+
+static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ int i;
+ pud_t *pud;
+ unsigned long addr;
+ unsigned long next;
+ struct lru_gen_mm_walk *priv = walk->private;
+
+ VM_BUG_ON(p4d_leaf(*p4d));
+
+ pud = pud_offset(p4d, start & P4D_MASK);
+restart:
+ for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
+ pud_t val = READ_ONCE(pud[i]);
+
+ next = pud_addr_end(addr, end);
+
+ if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val)))
+ continue;
+
+ walk_pmd_range(&val, addr, next, walk);
+
+ if (priv->batched >= MAX_LRU_BATCH) {
+ end = (addr | ~PUD_MASK) + 1;
+ goto done;
+ }
+ }
+
+ if (i < PTRS_PER_PUD && get_next_vma(walk, P4D_MASK, PUD_SIZE, &start, &end))
+ goto restart;
+
+ end = round_up(end, P4D_SIZE);
+done:
+ /* rounded-up boundaries can wrap to 0 */
+ priv->next_addr = end && walk->vma ? max(end, walk->vma->vm_start) : 0;
+
+ return -EAGAIN;
+}
+
+static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
+{
+ static const struct mm_walk_ops mm_walk_ops = {
+ .test_walk = should_skip_vma,
+ .p4d_entry = walk_pud_range,
+ };
+
+ int err;
+ struct mem_cgroup *memcg = lruvec_memcg(lruvec);
+
+ walk->next_addr = FIRST_USER_ADDRESS;
+
+ do {
+ err = -EBUSY;
+
+ /* folio_update_gen() requires stable folio_memcg() */
+ if (!mem_cgroup_trylock_pages(memcg))
+ break;
+
+ /* the caller might be holding the lock for write */
+ if (mmap_read_trylock(mm)) {
+ unsigned long start = walk->next_addr;
+ unsigned long end = mm->highest_vm_end;
+
+ err = walk_page_range(mm, start, end, &mm_walk_ops, walk);
+
+ mmap_read_unlock(mm);
+
+ if (walk->batched) {
+ spin_lock_irq(&lruvec->lru_lock);
+ reset_batch_size(lruvec, walk);
+ spin_unlock_irq(&lruvec->lru_lock);
+ }
+ }
+
+ mem_cgroup_unlock_pages();
+
+ cond_resched();
+ } while (err == -EAGAIN && walk->next_addr && !mm_is_oom_victim(mm));
+}
+
+static struct lru_gen_mm_walk *alloc_mm_walk(void)
+{
+ if (current->reclaim_state && current->reclaim_state->mm_walk)
+ return current->reclaim_state->mm_walk;
+
+ return kzalloc(sizeof(struct lru_gen_mm_walk),
+ __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
+}
+
+static void free_mm_walk(struct lru_gen_mm_walk *walk)
+{
+ if (!current->reclaim_state || !current->reclaim_state->mm_walk)
+ kfree(walk);
+}
+
static void inc_min_seq(struct lruvec *lruvec)
{
int type;
@@ -3287,7 +4127,7 @@ next:
return success;
}
-static void inc_max_seq(struct lruvec *lruvec, unsigned long max_seq)
+static void inc_max_seq(struct lruvec *lruvec)
{
int prev, next;
int type, zone;
@@ -3297,9 +4137,6 @@ static void inc_max_seq(struct lruvec *l
VM_BUG_ON(!seq_is_valid(lruvec));
- if (max_seq != lrugen->max_seq)
- goto unlock;
-
inc_min_seq(lruvec);
/*
@@ -3331,10 +4168,72 @@ static void inc_max_seq(struct lruvec *l
/* make sure preceding modifications appear */
smp_store_release(&lrugen->max_seq, lrugen->max_seq + 1);
-unlock:
+
spin_unlock_irq(&lruvec->lru_lock);
}
+static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
+ struct scan_control *sc, bool can_swap, bool full_scan)
+{
+ bool success;
+ struct lru_gen_mm_walk *walk;
+ struct mm_struct *mm = NULL;
+ struct lru_gen_struct *lrugen = &lruvec->lrugen;
+
+ VM_BUG_ON(max_seq > READ_ONCE(lrugen->max_seq));
+
+ /*
+ * If the hardware doesn't automatically set the accessed bit, fallback
+ * to lru_gen_look_around(), which only clears the accessed bit in a
+ * handful of PTEs. Spreading the work out over a period of time usually
+ * is less efficient, but it avoids bursty page faults.
+ */
+ if (!full_scan && !arch_has_hw_pte_young()) {
+ success = iterate_mm_list_nowalk(lruvec, max_seq);
+ goto done;
+ }
+
+ walk = alloc_mm_walk();
+ if (!walk) {
+ success = iterate_mm_list_nowalk(lruvec, max_seq);
+ goto done;
+ }
+
+ walk->lruvec = lruvec;
+ walk->max_seq = max_seq;
+ walk->can_swap = can_swap;
+ walk->full_scan = full_scan;
+
+ do {
+ success = iterate_mm_list(lruvec, walk, &mm);
+ if (mm)
+ walk_mm(lruvec, mm, walk);
+
+ cond_resched();
+ } while (mm);
+
+ free_mm_walk(walk);
+done:
+ if (!success) {
+ if (!current_is_kswapd() && !sc->priority)
+ wait_event_killable(lruvec->mm_state.wait,
+ max_seq < READ_ONCE(lrugen->max_seq));
+
+ return max_seq < READ_ONCE(lrugen->max_seq);
+ }
+
+ VM_BUG_ON(max_seq != READ_ONCE(lrugen->max_seq));
+
+ inc_max_seq(lruvec);
+ /* either this sees any waiters or they will see updated max_seq */
+ if (wq_has_sleeper(&lruvec->mm_state.wait))
+ wake_up_all(&lruvec->mm_state.wait);
+
+ wakeup_flusher_threads(WB_REASON_VMSCAN);
+
+ return true;
+}
+
static long get_nr_evictable(struct lruvec *lruvec, unsigned long max_seq,
unsigned long *min_seq, bool can_swap, bool *need_aging)
{
@@ -3416,7 +4315,7 @@ static void age_lruvec(struct lruvec *lr
nr_to_scan++;
if (nr_to_scan && need_aging && (!mem_cgroup_below_low(memcg) || sc->memcg_low_reclaim))
- inc_max_seq(lruvec, max_seq);
+ try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false);
}
static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
@@ -3425,6 +4324,8 @@ static void lru_gen_age_node(struct pgli
VM_BUG_ON(!current_is_kswapd());
+ current->reclaim_state->mm_walk = &pgdat->mm_walk;
+
memcg = mem_cgroup_iter(NULL, NULL, NULL);
do {
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
@@ -3433,11 +4334,16 @@ static void lru_gen_age_node(struct pgli
cond_resched();
} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)));
+
+ current->reclaim_state->mm_walk = NULL;
}
/*
* This function exploits spatial locality when shrink_page_list() walks the
* rmap. It scans the adjacent PTEs of a young PTE and promotes hot pages.
+ * If the scan was done cacheline efficiently, it adds the PMD entry pointing
+ * to the PTE table to the Bloom filter. This process is a feedback loop from
+ * the eviction to the aging.
*/
void lru_gen_look_around(struct page_vma_mapped_walk *pvmw)
{
@@ -3446,6 +4352,8 @@ void lru_gen_look_around(struct page_vma
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)] = {};
struct folio *folio = pfn_folio(pvmw->pfn);
struct mem_cgroup *memcg = folio_memcg(folio);
@@ -3507,6 +4415,8 @@ void lru_gen_look_around(struct page_vma
if (!ptep_test_and_clear_young(pvmw->vma, addr, pte + i))
continue;
+ young++;
+
if (pte_dirty(pte[i]) && !folio_test_dirty(folio) &&
!(folio_test_anon(folio) && folio_test_swapbacked(folio) &&
!folio_test_swapcache(folio)))
@@ -3522,7 +4432,13 @@ void lru_gen_look_around(struct page_vma
arch_leave_lazy_mmu_mode();
rcu_read_unlock();
- if (bitmap_weight(bitmap, MIN_LRU_BATCH) < PAGEVEC_SIZE) {
+ /* feedback from rmap walkers to page table walkers */
+ if (suitable_to_scan(i, young))
+ update_bloom_filter(lruvec, max_seq, pvmw->pmd);
+
+ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
+
+ 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);
@@ -3534,8 +4450,10 @@ void lru_gen_look_around(struct page_vma
if (!mem_cgroup_trylock_pages(memcg))
return;
- spin_lock_irq(&lruvec->lru_lock);
- new_gen = lru_gen_from_seq(lruvec->lrugen.max_seq);
+ 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]));
@@ -3546,10 +4464,14 @@ void lru_gen_look_around(struct page_vma
if (old_gen < 0 || old_gen == new_gen)
continue;
- lru_gen_update_size(lruvec, folio, old_gen, new_gen);
+ if (walk)
+ update_batch_size(walk, folio, old_gen, new_gen);
+ else
+ lru_gen_update_size(lruvec, folio, old_gen, new_gen);
}
- spin_unlock_irq(&lruvec->lru_lock);
+ if (!walk)
+ spin_unlock_irq(&lruvec->lru_lock);
mem_cgroup_unlock_pages();
}
@@ -3816,6 +4738,7 @@ static int evict_folios(struct lruvec *l
struct folio *folio;
enum vm_event_item item;
struct reclaim_stat stat;
+ struct lru_gen_mm_walk *walk;
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
@@ -3855,6 +4778,10 @@ static int evict_folios(struct lruvec *l
move_pages_to_lru(lruvec, &list);
+ walk = current->reclaim_state ? current->reclaim_state->mm_walk : NULL;
+ if (walk && walk->batched)
+ reset_batch_size(lruvec, walk);
+
item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
if (!cgroup_reclaim(sc))
__count_vm_events(item, reclaimed);
@@ -3909,20 +4836,25 @@ static long get_nr_to_scan(struct lruvec
return 0;
}
- inc_max_seq(lruvec, max_seq);
+ if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false))
+ return nr_to_scan;
- return nr_to_scan;
+ return min_seq[LRU_GEN_FILE] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0;
}
static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
{
struct blk_plug plug;
long scanned = 0;
+ struct pglist_data *pgdat = lruvec_pgdat(lruvec);
lru_add_drain();
blk_start_plug(&plug);
+ if (current_is_kswapd())
+ current->reclaim_state->mm_walk = &pgdat->mm_walk;
+
while (true) {
int delta;
int swappiness;
@@ -3950,6 +4882,9 @@ static void lru_gen_shrink_lruvec(struct
cond_resched();
}
+ if (current_is_kswapd())
+ current->reclaim_state->mm_walk = NULL;
+
blk_finish_plug(&plug);
}
@@ -3966,15 +4901,21 @@ void lru_gen_init_lruvec(struct lruvec *
for_each_gen_type_zone(gen, type, zone)
INIT_LIST_HEAD(&lrugen->lists[gen][type][zone]);
+
+ lruvec->mm_state.seq = MIN_NR_GENS;
+ init_waitqueue_head(&lruvec->mm_state.wait);
}
#ifdef CONFIG_MEMCG
void lru_gen_init_memcg(struct mem_cgroup *memcg)
{
+ INIT_LIST_HEAD(&memcg->mm_list.fifo);
+ spin_lock_init(&memcg->mm_list.lock);
}
void lru_gen_exit_memcg(struct mem_cgroup *memcg)
{
+ int i;
int nid;
for_each_node(nid) {
@@ -3982,6 +4923,11 @@ void lru_gen_exit_memcg(struct mem_cgrou
VM_BUG_ON(memchr_inv(lruvec->lrugen.nr_pages, 0,
sizeof(lruvec->lrugen.nr_pages)));
+
+ for (i = 0; i < NR_BLOOM_FILTERS; i++) {
+ bitmap_free(lruvec->mm_state.filters[i]);
+ lruvec->mm_state.filters[i] = NULL;
+ }
}
}
#endif
@@ -3990,6 +4936,7 @@ static int __init init_lru_gen(void)
{
BUILD_BUG_ON(MIN_NR_GENS + 1 >= MAX_NR_GENS);
BUILD_BUG_ON(BIT(LRU_GEN_WIDTH) <= MAX_NR_GENS);
+ BUILD_BUG_ON(sizeof(MM_STAT_CODES) != NR_MM_STATS + 1);
return 0;
};
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-x86-arm64-add-arch_has_hw_pte_young.patch
mm-x86-add-config_arch_has_nonleaf_pmd_young.patch
mm-vmscanc-refactor-shrink_node.patch
revert-include-linux-mm_inlineh-fold-__update_lru_size-into-its-sole-caller.patch
mm-multi-gen-lru-groundwork.patch
mm-multi-gen-lru-minimal-implementation.patch
mm-multi-gen-lru-exploit-locality-in-rmap.patch
mm-multi-gen-lru-support-page-table-walks.patch
mm-multi-gen-lru-optimize-multiple-memcgs.patch
mm-multi-gen-lru-kill-switch.patch
mm-multi-gen-lru-thrashing-prevention.patch
mm-multi-gen-lru-debugfs-interface.patch
mm-multi-gen-lru-admin-guide.patch
mm-multi-gen-lru-design-doc.patch
