A reaccess refers to detecting an access on a page via refault or access bit harvesting after the initial access. Similar to the working set histogram, the reaccess histogram breaks down reaccesses into user-defined bins.
It tracks reaccesses from MGLRU walks, where a move from older generations to the young generation counts as a reaccess. Swapped out pages are tracked with the generation number encoded in mm/workingset.c, and additional tracking is added for enabled memory cgroups to track an additional 4 swapped out generations.
Memcg interfaces: /sys/fs/cgroup/.../memory.workingset.reaccess The format is identical to memory.workingset.page_age, but the content breaks down reaccesses into pre-defined intervals. e.g. N0 1000 anon=6330 file=0 2000 anon=72 file=0 4000 anon=0 file=0 18446744073709551615 anon=0 file=0 N1 18446744073709551615 anon=0 file=0
/sys/fs/cgroup/.../memory.workingset.reaccess_intervals Defines the per-node intervals for memory.workingset.reaccess. e.g. echo N0=120000,240000,480000 > memory.workingset.reaccess_intervals
Signed-off-by: Yuanchu Xie yuanchu@google.com --- include/linux/workingset_report.h | 20 +++ mm/internal.h | 28 ++++ mm/memcontrol.c | 112 ++++++++++++++ mm/vmscan.c | 8 +- mm/workingset.c | 9 +- mm/workingset_report.c | 249 ++++++++++++++++++++++++++++++ 6 files changed, 419 insertions(+), 7 deletions(-)
diff --git a/include/linux/workingset_report.h b/include/linux/workingset_report.h index 502542c812b3..e908c5678b1e 100644 --- a/include/linux/workingset_report.h +++ b/include/linux/workingset_report.h @@ -4,6 +4,7 @@
#include <linux/types.h> #include <linux/mutex.h> +#include <linux/rcutree.h>
struct mem_cgroup; struct pglist_data; @@ -19,6 +20,12 @@ struct cgroup_file; #define WORKINGSET_INTERVAL_MAX ((unsigned long)-1) #define ANON_AND_FILE 2
+/* + * MAX_NR_EVICTED_GENS is set to 4 so we can track the same number of + * generations as MGLRU has resident. + */ +#define MAX_NR_EVICTED_GENS 4 + struct wsr_report_bin { unsigned long idle_age; unsigned long nr_pages[ANON_AND_FILE]; @@ -35,6 +42,18 @@ struct wsr_page_age_histo { struct wsr_report_bins bins; };
+struct wsr_evicted_gen { + unsigned long timestamp; + int seq; +}; + +struct wsr_reaccess_histo { + struct rcu_head rcu; + /* evicted gens start from min_seq[LRU_GEN_ANON] - 1 */ + struct wsr_evicted_gen gens[MAX_NR_EVICTED_GENS]; + struct wsr_report_bins bins; +}; + struct wsr_state { unsigned long report_threshold; unsigned long refresh_interval; @@ -47,6 +66,7 @@ struct wsr_state { /* breakdown of workingset by page age */ struct mutex page_age_lock; struct wsr_page_age_histo *page_age; + struct wsr_reaccess_histo __rcu *reaccess; };
void wsr_init(struct lruvec *lruvec); diff --git a/mm/internal.h b/mm/internal.h index 3730c8399ad4..077340b526e8 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -205,16 +205,44 @@ void putback_lru_page(struct page *page); void folio_putback_lru(struct folio *folio); extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
+/* + * in mm/workingset.c + */ +#define WORKINGSET_SHIFT 1 +#define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \ + WORKINGSET_SHIFT + NODES_SHIFT + \ + MEM_CGROUP_ID_SHIFT) +#define EVICTION_MASK (~0UL >> EVICTION_SHIFT) + #ifdef CONFIG_WORKINGSET_REPORT /* * in mm/wsr.c */ +void report_lru_gen_eviction(struct lruvec *lruvec, int type, int min_seq); +void lru_gen_report_reaccess(struct lruvec *lruvec, + struct lru_gen_mm_walk *walk); +void report_reaccess_refault(struct lruvec *lruvec, unsigned long token, + int type, int nr_pages); void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat); /* Requires wsr->page_age_lock held */ void wsr_refresh_scan(struct lruvec *lruvec, unsigned long refresh_interval); int workingset_report_intervals_parse(char *src, struct wsr_report_bins *bins); #else +struct lru_gen_mm_walk; +static inline void report_lru_gen_eviction(struct lruvec *lruvec, int type, + int min_seq) +{ +} +static inline void lru_gen_report_reaccess(struct lruvec *lruvec, + struct lru_gen_mm_walk *walk) +{ +} +static inline void report_reaccess_refault(struct lruvec *lruvec, + unsigned long token, int type, + int nr_pages) +{ +} static inline void notify_workingset(struct mem_cgroup *memcg, struct pglist_data *pgdat) { diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 75bda5f7994d..2a39a4445bb7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7108,6 +7108,71 @@ static ssize_t memory_ws_page_age_intervals_write(struct kernfs_open_file *of, return err; }
+static int memory_ws_reaccess_intervals_show(struct seq_file *m, void *v) +{ + int nid; + struct mem_cgroup *memcg = mem_cgroup_from_seq(m); + + for_each_node_state(nid, N_MEMORY) { + struct wsr_state *wsr; + struct wsr_reaccess_histo *reaccess; + int i, nr_bins; + + wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr; + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + if (!reaccess) + goto unlock; + seq_printf(m, "N%d=", nid); + nr_bins = reaccess->bins.nr_bins; + for (i = 0; i < nr_bins; ++i) { + struct wsr_report_bin *bin = &reaccess->bins.bins[i]; + + seq_printf(m, "%u", jiffies_to_msecs(bin->idle_age)); + if (i + 1 < nr_bins) + seq_putc(m, ','); + } + seq_putc(m, ' '); +unlock: + rcu_read_unlock(); + } + seq_putc(m, '\n'); + + return 0; +} + +static ssize_t memory_ws_reaccess_intervals_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + unsigned int nid; + int err; + struct wsr_state *wsr; + struct wsr_reaccess_histo *reaccess = NULL, *old; + struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); + + reaccess = kzalloc(sizeof(struct wsr_reaccess_histo), GFP_KERNEL); + if (!reaccess) + return -ENOMEM; + + err = memory_wsr_interval_parse(of, buf, nbytes, &nid, &reaccess->bins); + if (err < 0) + goto failed; + + if (err == 0) { + kfree(reaccess); + reaccess = NULL; + } + + wsr = &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr; + old = xchg(&wsr->reaccess, reaccess); + kfree_rcu(old, rcu); + return nbytes; +failed: + kfree(reaccess); + return err; +} + static int memory_ws_refresh_interval_show(struct seq_file *m, void *v) { int nid; @@ -7242,6 +7307,42 @@ static int memory_ws_page_age_show(struct seq_file *m, void *v)
return 0; } + +static int memory_ws_reaccess_histogram_show(struct seq_file *m, void *v) +{ + int nid; + struct mem_cgroup *memcg = mem_cgroup_from_seq(m); + + for_each_node_state(nid, N_MEMORY) { + struct wsr_state *wsr = + &mem_cgroup_lruvec(memcg, NODE_DATA(nid))->wsr; + struct wsr_reaccess_histo *reaccess; + struct wsr_report_bin *bin; + + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + + if (!reaccess) + goto unlock; + + wsr_refresh_report(wsr, memcg, NODE_DATA(nid)); + + seq_printf(m, "N%d\n", nid); + for (bin = reaccess->bins.bins; + bin->idle_age != WORKINGSET_INTERVAL_MAX; bin++) + seq_printf(m, "%u anon=%lu file=%lu\n", + jiffies_to_msecs(bin->idle_age), + bin->nr_pages[0], bin->nr_pages[1]); + + seq_printf(m, "%lu anon=%lu file=%lu\n", WORKINGSET_INTERVAL_MAX, + bin->nr_pages[0], bin->nr_pages[1]); + +unlock: + rcu_read_unlock(); + } + + return 0; +} #endif
static struct cftype memory_files[] = { @@ -7337,6 +7438,17 @@ static struct cftype memory_files[] = { .file_offset = offsetof(struct mem_cgroup, workingset_page_age_file), .seq_show = memory_ws_page_age_show, }, + { + .name = "workingset.reaccess_intervals", + .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE, + .seq_show = memory_ws_reaccess_intervals_show, + .write = memory_ws_reaccess_intervals_write, + }, + { + .name = "workingset.reaccess", + .flags = CFTYPE_NOT_ON_ROOT | CFTYPE_NS_DELEGATABLE, + .seq_show = memory_ws_reaccess_histogram_show, + }, #endif {} /* terminate */ }; diff --git a/mm/vmscan.c b/mm/vmscan.c index c6acd5265b3f..4d9245e2c0d1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3637,6 +3637,7 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_ mem_cgroup_unlock_pages();
if (walk->batched) { + lru_gen_report_reaccess(lruvec, walk); spin_lock_irq(&lruvec->lru_lock); reset_batch_size(lruvec, walk); spin_unlock_irq(&lruvec->lru_lock); @@ -3709,6 +3710,7 @@ static bool inc_min_seq(struct lruvec *lruvec, int type, bool can_swap) } done: reset_ctrl_pos(lruvec, type, true); + report_lru_gen_eviction(lruvec, type, lrugen->min_seq[type] + 1); WRITE_ONCE(lrugen->min_seq[type], lrugen->min_seq[type] + 1);
return true; @@ -3750,6 +3752,7 @@ static bool try_to_inc_min_seq(struct lruvec *lruvec, bool can_swap) continue;
reset_ctrl_pos(lruvec, type, true); + report_lru_gen_eviction(lruvec, type, min_seq[type]); WRITE_ONCE(lrugen->min_seq[type], min_seq[type]); success = true; } @@ -4565,11 +4568,14 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap sc->nr_scanned -= folio_nr_pages(folio); }
+ walk = current->reclaim_state->mm_walk; + if (walk && walk->batched) + lru_gen_report_reaccess(lruvec, walk); + spin_lock_irq(&lruvec->lru_lock);
move_folios_to_lru(lruvec, &list);
- walk = current->reclaim_state->mm_walk; if (walk && walk->batched) reset_batch_size(lruvec, walk);
diff --git a/mm/workingset.c b/mm/workingset.c index 226012974328..057fbedd91ea 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -17,6 +17,8 @@ #include <linux/fs.h> #include <linux/mm.h>
+#include "internal.h" + /* * Double CLOCK lists * @@ -179,12 +181,6 @@ * refault distance will immediately activate the refaulting page. */
-#define WORKINGSET_SHIFT 1 -#define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) + \ - WORKINGSET_SHIFT + NODES_SHIFT + \ - MEM_CGROUP_ID_SHIFT) -#define EVICTION_MASK (~0UL >> EVICTION_SHIFT) - /* * Eviction timestamps need to be able to cover the full range of * actionable refaults. However, bits are tight in the xarray @@ -294,6 +290,7 @@ static void lru_gen_refault(struct folio *folio, void *shadow) goto unlock;
mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta); + report_reaccess_refault(lruvec, token, type, delta);
if (!recent) goto unlock; diff --git a/mm/workingset_report.c b/mm/workingset_report.c index b00ffbfebcab..504d840bbe6a 100644 --- a/mm/workingset_report.c +++ b/mm/workingset_report.c @@ -34,6 +34,7 @@ void wsr_destroy(struct lruvec *lruvec)
mutex_destroy(&wsr->page_age_lock); kfree(wsr->page_age); + kfree_rcu(wsr->reaccess, rcu); memset(wsr, 0, sizeof(*wsr)); }
@@ -259,6 +260,254 @@ bool wsr_refresh_report(struct wsr_state *wsr, struct mem_cgroup *root, } EXPORT_SYMBOL_GPL(wsr_refresh_report);
+static void lru_gen_collect_reaccess_refault(struct wsr_report_bins *bins, + unsigned long timestamp, int type, + int nr_pages) +{ + unsigned long curr_timestamp = jiffies; + struct wsr_report_bin *bin = &bins->bins[0]; + + while (bin->idle_age != WORKINGSET_INTERVAL_MAX && + time_before(timestamp + bin->idle_age, curr_timestamp)) + bin++; + + bin->nr_pages[type] += nr_pages; +} + +static void collect_reaccess_type(struct lru_gen_mm_walk *walk, + const struct lru_gen_folio *lrugen, + struct wsr_report_bin *bin, + unsigned long max_seq, unsigned long min_seq, + unsigned long curr_timestamp, int type) +{ + unsigned long seq; + + /* Skip max_seq because a reaccess moves a page from another seq + * to max_seq. We use the negative change in page count from + * other seqs to track the number of reaccesses. + */ + for (seq = max_seq - 1; seq + 1 > min_seq; seq--) { + int younger_gen, gen, zone; + unsigned long gen_end, gen_start; + long delta = 0; + + gen = lru_gen_from_seq(seq); + + for (zone = 0; zone < MAX_NR_ZONES; zone++) { + long nr_pages = walk->nr_pages[gen][type][zone]; + + if (nr_pages < 0) + delta += -nr_pages; + } + + gen_end = READ_ONCE(lrugen->timestamps[gen]); + younger_gen = lru_gen_from_seq(seq + 1); + gen_start = READ_ONCE(lrugen->timestamps[younger_gen]); + + /* ensure gen_start is within idle_age of bin */ + while (bin->idle_age != WORKINGSET_INTERVAL_MAX && + time_before(gen_start + bin->idle_age, curr_timestamp)) + bin++; + + while (bin->idle_age != WORKINGSET_INTERVAL_MAX && + time_before(gen_end + bin->idle_age, curr_timestamp)) { + unsigned long proportion = (long)gen_start - + (long)curr_timestamp + + (long)bin->idle_age; + unsigned long gen_len = (long)gen_start - (long)gen_end; + + if (!gen_len) + break; + if (proportion) { + unsigned long split_bin = + delta / gen_len * proportion; + bin->nr_pages[type] += split_bin; + delta -= split_bin; + } + gen_start = curr_timestamp - bin->idle_age; + bin++; + } + bin->nr_pages[type] += delta; + } +} + +/* + * Reaccesses are propagated up the memcg hierarchy during scanning/refault. + * Collect the reaccess information from a multi-gen LRU walk. + */ +static void lru_gen_collect_reaccess(struct wsr_report_bins *bins, + struct lru_gen_folio *lrugen, + struct lru_gen_mm_walk *walk) +{ + int type; + unsigned long curr_timestamp = jiffies; + unsigned long max_seq = READ_ONCE(walk->max_seq); + unsigned long min_seq[ANON_AND_FILE] = { + READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]), + READ_ONCE(lrugen->min_seq[LRU_GEN_FILE]), + }; + + for (type = 0; type < ANON_AND_FILE; type++) { + struct wsr_report_bin *bin = &bins->bins[0]; + + collect_reaccess_type(walk, lrugen, bin, max_seq, + min_seq[type], curr_timestamp, type); + } +} + +void lru_gen_report_reaccess(struct lruvec *lruvec, struct lru_gen_mm_walk *walk) +{ + struct lru_gen_folio *lrugen = &lruvec->lrugen; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + + for (memcg = lruvec_memcg(lruvec); memcg; + memcg = parent_mem_cgroup(memcg)) { + struct lruvec *memcg_lruvec = + mem_cgroup_lruvec(memcg, lruvec_pgdat(lruvec)); + struct wsr_state *wsr = &memcg_lruvec->wsr; + struct wsr_reaccess_histo *reaccess; + + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + if (!reaccess) { + rcu_read_unlock(); + continue; + } + lru_gen_collect_reaccess(&reaccess->bins, lrugen, walk); + rcu_read_unlock(); + } +} + +static inline int evicted_gen_from_seq(unsigned long seq) +{ + return seq % MAX_NR_EVICTED_GENS; +} + +void report_lru_gen_eviction(struct lruvec *lruvec, int type, int min_seq) +{ + int seq; + struct wsr_reaccess_histo *reaccess = NULL; + struct lru_gen_folio *lrugen = &lruvec->lrugen; + struct wsr_state *wsr = &lruvec->wsr; + + /* + * Since file can go ahead of anon, min_seq[file] >= min_seq[anon] + * only record evictions when anon moves forward. + */ + if (type != LRU_GEN_ANON) + return; + + /* + * lru_lock is held during eviction, so reaccess accounting + * can be serialized. + */ + lockdep_assert_held(&lruvec->lru_lock); + + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + if (!reaccess) + goto unlock; + + for (seq = READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]); seq < min_seq; + ++seq) { + int evicted_gen = evicted_gen_from_seq(seq); + int gen = lru_gen_from_seq(seq); + + WRITE_ONCE(reaccess->gens[evicted_gen].seq, seq); + WRITE_ONCE(reaccess->gens[evicted_gen].timestamp, + READ_ONCE(lrugen->timestamps[gen])); + } + +unlock: + rcu_read_unlock(); +} + +/* + * May yield an incorrect timestamp if the token collides with + * a recently evicted generation. + */ +static int timestamp_from_workingset_token(struct lruvec *lruvec, + unsigned long token, + unsigned long *timestamp) +{ + int type, err = -EEXIST; + unsigned long seq, evicted_min_seq; + struct wsr_reaccess_histo *reaccess = NULL; + struct lru_gen_folio *lrugen = &lruvec->lrugen; + struct wsr_state *wsr = &lruvec->wsr; + unsigned long min_seq[ANON_AND_FILE] = { + READ_ONCE(lrugen->min_seq[LRU_GEN_ANON]), + READ_ONCE(lrugen->min_seq[LRU_GEN_FILE]) + }; + + token >>= LRU_REFS_WIDTH; + + /* recent eviction */ + for (type = 0; type < ANON_AND_FILE; ++type) { + if (token == + (min_seq[type] & (EVICTION_MASK >> LRU_REFS_WIDTH))) { + int gen = lru_gen_from_seq(min_seq[type]); + + *timestamp = READ_ONCE(lrugen->timestamps[gen]); + return 0; + } + } + + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + if (!reaccess) + goto unlock; + + /* look up in evicted gen buffer */ + evicted_min_seq = min_seq[LRU_GEN_ANON] - MAX_NR_EVICTED_GENS; + if (min_seq[LRU_GEN_ANON] < MAX_NR_EVICTED_GENS) + evicted_min_seq = 0; + for (seq = min_seq[LRU_GEN_ANON]; seq > evicted_min_seq; --seq) { + int gen = evicted_gen_from_seq(seq - 1); + + if (token == (reaccess->gens[gen].seq & + (EVICTION_MASK >> LRU_REFS_WIDTH))) { + *timestamp = reaccess->gens[gen].timestamp; + + goto unlock; + } + } + +unlock: + rcu_read_unlock(); + return err; +} + +void report_reaccess_refault(struct lruvec *lruvec, unsigned long token, + int type, int nr_pages) +{ + unsigned long timestamp; + int err; + struct mem_cgroup *memcg = lruvec_memcg(lruvec); + + err = timestamp_from_workingset_token(lruvec, token, ×tamp); + if (err) + return; + + for (memcg = lruvec_memcg(lruvec); memcg; + memcg = parent_mem_cgroup(memcg)) { + struct lruvec *memcg_lruvec = + mem_cgroup_lruvec(memcg, lruvec_pgdat(lruvec)); + struct wsr_state *wsr = &memcg_lruvec->wsr; + struct wsr_reaccess_histo *reaccess = NULL; + + rcu_read_lock(); + reaccess = rcu_dereference(wsr->reaccess); + if (!reaccess) { + rcu_read_unlock(); + continue; + } + lru_gen_collect_reaccess_refault(&reaccess->bins, timestamp, + type, nr_pages); + rcu_read_unlock(); + } +} + static struct pglist_data *kobj_to_pgdat(struct kobject *kobj) { int nid = IS_ENABLED(CONFIG_NUMA) ? kobj_to_dev(kobj)->id :