Add /sys/kernel/debug/lru_gen for working set estimation and proactive reclaim. These techniques are commonly used to optimize job scheduling (bin packing) in data centers [1][2]. Compared with the page table-based approach and the PFN-based approach, this lruvec-based approach has the following advantages: 1. It offers better choices because it is aware of memcgs, NUMA nodes, shared mappings and unmapped page cache. 2. It is more scalable because it is O(nr_hot_pages), whereas the PFN-based approach is O(nr_total_pages). Add /sys/kernel/debug/lru_gen_full for debugging. [1] https://dl.acm.org/doi/10.1145/3297858.3304053 [2] https://dl.acm.org/doi/10.1145/3503222.3507731 Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx> Reviewed-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> 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> --- include/linux/nodemask.h | 1 + mm/vmscan.c | 411 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 402 insertions(+), 10 deletions(-) diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 4b71a96190a8..3a0eec9f2faa 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -493,6 +493,7 @@ static inline int num_node_state(enum node_states state) #define first_online_node 0 #define first_memory_node 0 #define next_online_node(nid) (MAX_NUMNODES) +#define next_memory_node(nid) (MAX_NUMNODES) #define nr_node_ids 1U #define nr_online_nodes 1U diff --git a/mm/vmscan.c b/mm/vmscan.c index 08727f3b7171..509989fb39ef 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -52,6 +52,7 @@ #include <linux/pagewalk.h> #include <linux/shmem_fs.h> #include <linux/ctype.h> +#include <linux/debugfs.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -4202,12 +4203,40 @@ static void clear_mm_walk(void) kfree(walk); } -static void inc_min_seq(struct lruvec *lruvec, int type) +static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap) { + int zone; + int remaining = MAX_LRU_BATCH; struct lru_gen_struct *lrugen = &lruvec->lrugen; + int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]); + if (type == LRU_GEN_ANON && !can_swap) + goto done; + + /* prevent cold/hot inversion if force_scan is true */ + for (zone = 0; zone < MAX_NR_ZONES; zone++) { + struct list_head *head = &lrugen->lists[old_gen][type][zone]; + + while (!list_empty(head)) { + struct folio *folio = lru_to_folio(head); + + VM_WARN_ON_ONCE_FOLIO(folio_test_unevictable(folio), folio); + VM_WARN_ON_ONCE_FOLIO(folio_test_active(folio), folio); + VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio); + VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio); + + new_gen = folio_inc_gen(lruvec, folio, false); + list_move_tail(&folio->lru, &lrugen->lists[new_gen][type][zone]); + + if (!--remaining) + return false; + } + } +done: reset_ctrl_pos(lruvec, type, true); WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1); + + return true; } static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) @@ -4253,7 +4282,7 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) return success; } -static void inc_max_seq(struct lruvec *lruvec, bool can_swap) +static void inc_max_seq(struct lruvec *lruvec, bool can_swap, bool force_scan) { int prev, next; int type, zone; @@ -4267,9 +4296,13 @@ static void inc_max_seq(struct lruvec *lruvec, bool can_swap) if (get_nr_gens(lruvec, type) != MAX_NR_GENS) continue; - VM_WARN_ON_ONCE(type == LRU_GEN_FILE || can_swap); + VM_WARN_ON_ONCE(!force_scan && (type == LRU_GEN_FILE || can_swap)); - inc_min_seq(lruvec, type); + while (!inc_min_seq(lruvec, type, can_swap)) { + spin_unlock_irq(&lruvec->lru_lock); + cond_resched(); + spin_lock_irq(&lruvec->lru_lock); + } } /* @@ -4306,7 +4339,7 @@ static void inc_max_seq(struct lruvec *lruvec, bool can_swap) } static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, - struct scan_control *sc, bool can_swap) + struct scan_control *sc, bool can_swap, bool force_scan) { bool success; struct lru_gen_mm_walk *walk; @@ -4327,7 +4360,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, * handful of PTEs. Spreading the work out over a period of time usually * is less efficient, but it avoids bursty page faults. */ - if (!(arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))) { + if (!force_scan && !(arch_has_hw_pte_young() && get_cap(LRU_GEN_MM_WALK))) { success = iterate_mm_list_nowalk(lruvec, max_seq); goto done; } @@ -4341,7 +4374,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, walk->lruvec = lruvec; walk->max_seq = max_seq; walk->can_swap = can_swap; - walk->force_scan = false; + walk->force_scan = force_scan; do { success = iterate_mm_list(lruvec, walk, &mm); @@ -4361,7 +4394,7 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq, VM_WARN_ON_ONCE(max_seq != READ_ONCE(lrugen->max_seq)); - inc_max_seq(lruvec, can_swap); + inc_max_seq(lruvec, can_swap, force_scan); /* 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); @@ -4460,7 +4493,7 @@ static bool age_lruvec(struct lruvec *lruvec, struct scan_control *sc, unsigned } if (nr_to_scan && need_aging) - try_to_inc_max_seq(lruvec, max_seq, sc, swappiness); + try_to_inc_max_seq(lruvec, max_seq, sc, swappiness, false); return true; } @@ -5041,7 +5074,7 @@ static unsigned long get_nr_to_scan(struct lruvec *lruvec, struct scan_control * if (current_is_kswapd()) return 0; - if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap)) + if (try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, false)) return nr_to_scan; done: return min_seq[!can_swap] + MIN_NR_GENS <= max_seq ? nr_to_scan : 0; @@ -5330,6 +5363,361 @@ static struct attribute_group lru_gen_attr_group = { .attrs = lru_gen_attrs, }; +/****************************************************************************** + * debugfs interface + ******************************************************************************/ + +static void *lru_gen_seq_start(struct seq_file *m, loff_t *pos) +{ + struct mem_cgroup *memcg; + loff_t nr_to_skip = *pos; + + m->private = kvmalloc(PATH_MAX, GFP_KERNEL); + if (!m->private) + return ERR_PTR(-ENOMEM); + + memcg = mem_cgroup_iter(NULL, NULL, NULL); + do { + int nid; + + for_each_node_state(nid, N_MEMORY) { + if (!nr_to_skip--) + return get_lruvec(memcg, nid); + } + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); + + return NULL; +} + +static void lru_gen_seq_stop(struct seq_file *m, void *v) +{ + if (!IS_ERR_OR_NULL(v)) + mem_cgroup_iter_break(NULL, lruvec_memcg(v)); + + kvfree(m->private); + m->private = NULL; +} + +static void *lru_gen_seq_next(struct seq_file *m, void *v, loff_t *pos) +{ + int nid = lruvec_pgdat(v)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(v); + + ++*pos; + + nid = next_memory_node(nid); + if (nid == MAX_NUMNODES) { + memcg = mem_cgroup_iter(NULL, memcg, NULL); + if (!memcg) + return NULL; + + nid = first_memory_node; + } + + return get_lruvec(memcg, nid); +} + +static void lru_gen_seq_show_full(struct seq_file *m, struct lruvec *lruvec, + unsigned long max_seq, unsigned long *min_seq, + unsigned long seq) +{ + int i; + int type, tier; + int hist = lru_hist_from_seq(seq); + struct lru_gen_struct *lrugen = &lruvec->lrugen; + + for (tier = 0; tier < MAX_NR_TIERS; tier++) { + seq_printf(m, " %10d", tier); + for (type = 0; type < ANON_AND_FILE; type++) { + const char *s = " "; + unsigned long n[3] = {}; + + if (seq == max_seq) { + s = "RT "; + n[0] = READ_ONCE(lrugen->avg_refaulted[type][tier]); + n[1] = READ_ONCE(lrugen->avg_total[type][tier]); + } else if (seq == min_seq[type] || NR_HIST_GENS > 1) { + s = "rep"; + n[0] = atomic_long_read(&lrugen->refaulted[hist][type][tier]); + n[1] = atomic_long_read(&lrugen->evicted[hist][type][tier]); + if (tier) + n[2] = READ_ONCE(lrugen->protected[hist][type][tier - 1]); + } + + for (i = 0; i < 3; i++) + seq_printf(m, " %10lu%c", n[i], s[i]); + } + seq_putc(m, '\n'); + } + + seq_puts(m, " "); + for (i = 0; i < NR_MM_STATS; i++) { + const char *s = " "; + unsigned long n = 0; + + if (seq == max_seq && NR_HIST_GENS == 1) { + s = "LOYNFA"; + n = READ_ONCE(lruvec->mm_state.stats[hist][i]); + } else if (seq != max_seq && NR_HIST_GENS > 1) { + s = "loynfa"; + n = READ_ONCE(lruvec->mm_state.stats[hist][i]); + } + + seq_printf(m, " %10lu%c", n, s[i]); + } + seq_putc(m, '\n'); +} + +static int lru_gen_seq_show(struct seq_file *m, void *v) +{ + unsigned long seq; + bool full = !debugfs_real_fops(m->file)->write; + struct lruvec *lruvec = v; + struct lru_gen_struct *lrugen = &lruvec->lrugen; + int nid = lruvec_pgdat(lruvec)->node_id; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + if (nid == first_memory_node) { + const char *path = memcg ? m->private : ""; + +#ifdef CONFIG_MEMCG + if (memcg) + cgroup_path(memcg->css.cgroup, m->private, PATH_MAX); +#endif + seq_printf(m, "memcg %5hu %s\n", mem_cgroup_id(memcg), path); + } + + seq_printf(m, " node %5d\n", nid); + + if (!full) + seq = min_seq[LRU_GEN_ANON]; + else if (max_seq >= MAX_NR_GENS) + seq = max_seq - MAX_NR_GENS + 1; + else + seq = 0; + + for (; seq <= max_seq; seq++) { + int type, zone; + int gen = lru_gen_from_seq(seq); + unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]); + + seq_printf(m, " %10lu %10u", seq, jiffies_to_msecs(jiffies - birth)); + + for (type = 0; type < ANON_AND_FILE; type++) { + unsigned long size = 0; + char mark = full && seq < min_seq[type] ? 'x' : ' '; + + for (zone = 0; zone < MAX_NR_ZONES; zone++) + size += max(READ_ONCE(lrugen->nr_pages[gen][type][zone]), 0L); + + seq_printf(m, " %10lu%c", size, mark); + } + + seq_putc(m, '\n'); + + if (full) + lru_gen_seq_show_full(m, lruvec, max_seq, min_seq, seq); + } + + return 0; +} + +static const struct seq_operations lru_gen_seq_ops = { + .start = lru_gen_seq_start, + .stop = lru_gen_seq_stop, + .next = lru_gen_seq_next, + .show = lru_gen_seq_show, +}; + +static int run_aging(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + bool can_swap, bool force_scan) +{ + DEFINE_MAX_SEQ(lruvec); + DEFINE_MIN_SEQ(lruvec); + + if (seq < max_seq) + return 0; + + if (seq > max_seq) + return -EINVAL; + + if (!force_scan && min_seq[!can_swap] + MAX_NR_GENS - 1 <= max_seq) + return -ERANGE; + + try_to_inc_max_seq(lruvec, max_seq, sc, can_swap, force_scan); + + return 0; +} + +static int run_eviction(struct lruvec *lruvec, unsigned long seq, struct scan_control *sc, + int swappiness, unsigned long nr_to_reclaim) +{ + DEFINE_MAX_SEQ(lruvec); + + if (seq + MIN_NR_GENS > max_seq) + return -EINVAL; + + sc->nr_reclaimed = 0; + + while (!signal_pending(current)) { + DEFINE_MIN_SEQ(lruvec); + + if (seq < min_seq[!swappiness]) + return 0; + + if (sc->nr_reclaimed >= nr_to_reclaim) + return 0; + + if (!evict_folios(lruvec, sc, swappiness, NULL)) + return 0; + + cond_resched(); + } + + return -EINTR; +} + +static int run_cmd(char cmd, int memcg_id, int nid, unsigned long seq, + struct scan_control *sc, int swappiness, unsigned long opt) +{ + struct lruvec *lruvec; + int err = -EINVAL; + struct mem_cgroup *memcg = NULL; + + if (nid < 0 || nid >= MAX_NUMNODES || !node_state(nid, N_MEMORY)) + return -EINVAL; + + if (!mem_cgroup_disabled()) { + rcu_read_lock(); + memcg = mem_cgroup_from_id(memcg_id); +#ifdef CONFIG_MEMCG + if (memcg && !css_tryget(&memcg->css)) + memcg = NULL; +#endif + rcu_read_unlock(); + + if (!memcg) + return -EINVAL; + } + + if (memcg_id != mem_cgroup_id(memcg)) + goto done; + + lruvec = get_lruvec(memcg, nid); + + if (swappiness < 0) + swappiness = get_swappiness(lruvec, sc); + else if (swappiness > 200) + goto done; + + switch (cmd) { + case '+': + err = run_aging(lruvec, seq, sc, swappiness, opt); + break; + case '-': + err = run_eviction(lruvec, seq, sc, swappiness, opt); + break; + } +done: + mem_cgroup_put(memcg); + + return err; +} + +static ssize_t lru_gen_seq_write(struct file *file, const char __user *src, + size_t len, loff_t *pos) +{ + void *buf; + char *cur, *next; + unsigned int flags; + struct blk_plug plug; + int err = -EINVAL; + struct scan_control sc = { + .may_writepage = true, + .may_unmap = true, + .may_swap = true, + .reclaim_idx = MAX_NR_ZONES - 1, + .gfp_mask = GFP_KERNEL, + }; + + buf = kvmalloc(len + 1, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + if (copy_from_user(buf, src, len)) { + kvfree(buf); + return -EFAULT; + } + + set_task_reclaim_state(current, &sc.reclaim_state); + flags = memalloc_noreclaim_save(); + blk_start_plug(&plug); + if (!set_mm_walk(NULL)) { + err = -ENOMEM; + goto done; + } + + next = buf; + next[len] = '\0'; + + while ((cur = strsep(&next, ",;\n"))) { + int n; + int end; + char cmd; + unsigned int memcg_id; + unsigned int nid; + unsigned long seq; + unsigned int swappiness = -1; + unsigned long opt = -1; + + cur = skip_spaces(cur); + if (!*cur) + continue; + + n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid, + &seq, &end, &swappiness, &end, &opt, &end); + if (n < 4 || cur[end]) { + err = -EINVAL; + break; + } + + err = run_cmd(cmd, memcg_id, nid, seq, &sc, swappiness, opt); + if (err) + break; + } +done: + clear_mm_walk(); + blk_finish_plug(&plug); + memalloc_noreclaim_restore(flags); + set_task_reclaim_state(current, NULL); + + kvfree(buf); + + return err ? : len; +} + +static int lru_gen_seq_open(struct inode *inode, struct file *file) +{ + return seq_open(file, &lru_gen_seq_ops); +} + +static const struct file_operations lru_gen_rw_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .write = lru_gen_seq_write, + .llseek = seq_lseek, + .release = seq_release, +}; + +static const struct file_operations lru_gen_ro_fops = { + .open = lru_gen_seq_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, +}; + /****************************************************************************** * initialization ******************************************************************************/ @@ -5387,6 +5775,9 @@ static int __init init_lru_gen(void) if (sysfs_create_group(mm_kobj, &lru_gen_attr_group)) pr_err("lru_gen: failed to create sysfs group\n"); + debugfs_create_file("lru_gen", 0644, NULL, NULL, &lru_gen_rw_fops); + debugfs_create_file("lru_gen_full", 0444, NULL, NULL, &lru_gen_ro_fops); + return 0; }; late_initcall(init_lru_gen); -- 2.37.1.595.g718a3a8f04-goog
