From: SeongJae Park sjpark@amazon.de
mainline inclusion from mainline-5.15-rc1 commit b9a6ac4e4ede4172d165c133398b93e3233b0ba7 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I4GVMK CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
------------------------------------------------- Even somehow the initial monitoring target regions are well constructed to fulfill the assumption (pages in same region have similar access frequencies), the data access pattern can be dynamically changed. This will result in low monitoring quality. To keep the assumption as much as possible, DAMON adaptively merges and splits each region based on their access frequency.
For each ``aggregation interval``, it compares the access frequencies of adjacent regions and merges those if the frequency difference is small. Then, after it reports and clears the aggregated access frequency of each region, it splits each region into two or three regions if the total number of regions will not exceed the user-specified maximum number of regions after the split.
In this way, DAMON provides its best-effort quality and minimal overhead while keeping the upper-bound overhead that users set.
Link: https://lkml.kernel.org/r/20210716081449.22187-4-sj38.park@gmail.com Signed-off-by: SeongJae Park sjpark@amazon.de Reviewed-by: Leonard Foerster foersleo@amazon.de Reviewed-by: Fernand Sieber sieberf@amazon.com Acked-by: Shakeel Butt shakeelb@google.com Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: Amit Shah amit@kernel.org Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Brendan Higgins brendanhiggins@google.com Cc: David Hildenbrand david@redhat.com Cc: David Rientjes rientjes@google.com Cc: David Woodhouse dwmw@amazon.com Cc: Fan Du fan.du@intel.com Cc: Greg Kroah-Hartman greg@kroah.com Cc: Greg Thelen gthelen@google.com Cc: Ingo Molnar mingo@redhat.com Cc: Joe Perches joe@perches.com Cc: Jonathan Cameron Jonathan.Cameron@huawei.com Cc: Jonathan Corbet corbet@lwn.net Cc: Marco Elver elver@google.com Cc: Markus Boehme markubo@amazon.de Cc: Maximilian Heyne mheyne@amazon.de Cc: Mel Gorman mgorman@suse.de Cc: Minchan Kim minchan@kernel.org Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Rik van Riel riel@surriel.com Cc: Shuah Khan shuah@kernel.org Cc: Steven Rostedt (VMware) rostedt@goodmis.org Cc: Vladimir Davydov vdavydov.dev@gmail.com Cc: Vlastimil Babka vbabka@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org (cherry picked from commit b9a6ac4e4ede4172d165c133398b93e3233b0ba7) Signed-off-by: Yue Zou zouyue3@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- include/linux/damon.h | 30 ++++-- mm/damon/core.c | 224 ++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 237 insertions(+), 17 deletions(-)
diff --git a/include/linux/damon.h b/include/linux/damon.h index 67db309ad61b..ce2a84b26cd7 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -12,6 +12,9 @@ #include <linux/time64.h> #include <linux/types.h>
+/* Minimal region size. Every damon_region is aligned by this. */ +#define DAMON_MIN_REGION PAGE_SIZE + /** * struct damon_addr_range - Represents an address region of [@start, @end). * @start: Start address of the region (inclusive). @@ -39,6 +42,7 @@ struct damon_region { /** * struct damon_target - Represents a monitoring target. * @id: Unique identifier for this target. + * @nr_regions: Number of monitoring target regions of this target. * @regions_list: Head of the monitoring target regions of this target. * @list: List head for siblings. * @@ -50,6 +54,7 @@ struct damon_region { */ struct damon_target { unsigned long id; + unsigned int nr_regions; struct list_head regions_list; struct list_head list; }; @@ -85,6 +90,8 @@ struct damon_ctx; * prepared for the next access check. * @check_accesses should check the accesses to each region that made after the * last preparation and update the number of observed accesses of each region. + * It should also return max number of observed accesses that made as a result + * of its update. The value will be used for regions adjustment threshold. * @reset_aggregated should reset the access monitoring results that aggregated * by @check_accesses. * @target_valid should check whether the target is still valid for the @@ -95,7 +102,7 @@ struct damon_primitive { void (*init)(struct damon_ctx *context); void (*update)(struct damon_ctx *context); void (*prepare_access_checks)(struct damon_ctx *context); - void (*check_accesses)(struct damon_ctx *context); + unsigned int (*check_accesses)(struct damon_ctx *context); void (*reset_aggregated)(struct damon_ctx *context); bool (*target_valid)(void *target); void (*cleanup)(struct damon_ctx *context); @@ -172,7 +179,9 @@ struct damon_callback { * @primitive: Set of monitoring primitives for given use cases. * @callback: Set of callbacks for monitoring events notifications. * - * @region_targets: Head of monitoring targets (&damon_target) list. + * @min_nr_regions: The minimum number of adaptive monitoring regions. + * @max_nr_regions: The maximum number of adaptive monitoring regions. + * @adaptive_targets: Head of monitoring targets (&damon_target) list. */ struct damon_ctx { unsigned long sample_interval; @@ -191,7 +200,9 @@ struct damon_ctx { struct damon_primitive primitive; struct damon_callback callback;
- struct list_head region_targets; + unsigned long min_nr_regions; + unsigned long max_nr_regions; + struct list_head adaptive_targets; };
#define damon_next_region(r) \ @@ -207,28 +218,31 @@ struct damon_ctx { list_for_each_entry_safe(r, next, &t->regions_list, list)
#define damon_for_each_target(t, ctx) \ - list_for_each_entry(t, &(ctx)->region_targets, list) + list_for_each_entry(t, &(ctx)->adaptive_targets, list)
#define damon_for_each_target_safe(t, next, ctx) \ - list_for_each_entry_safe(t, next, &(ctx)->region_targets, list) + list_for_each_entry_safe(t, next, &(ctx)->adaptive_targets, list)
#ifdef CONFIG_DAMON
struct damon_region *damon_new_region(unsigned long start, unsigned long end); inline void damon_insert_region(struct damon_region *r, - struct damon_region *prev, struct damon_region *next); + struct damon_region *prev, struct damon_region *next, + struct damon_target *t); void damon_add_region(struct damon_region *r, struct damon_target *t); -void damon_destroy_region(struct damon_region *r); +void damon_destroy_region(struct damon_region *r, struct damon_target *t);
struct damon_target *damon_new_target(unsigned long id); void damon_add_target(struct damon_ctx *ctx, struct damon_target *t); void damon_free_target(struct damon_target *t); void damon_destroy_target(struct damon_target *t); +unsigned int damon_nr_regions(struct damon_target *t);
struct damon_ctx *damon_new_ctx(void); void damon_destroy_ctx(struct damon_ctx *ctx); int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int, - unsigned long aggr_int, unsigned long primitive_upd_int); + unsigned long aggr_int, unsigned long primitive_upd_int, + unsigned long min_nr_reg, unsigned long max_nr_reg);
int damon_start(struct damon_ctx **ctxs, int nr_ctxs); int damon_stop(struct damon_ctx **ctxs, int nr_ctxs); diff --git a/mm/damon/core.c b/mm/damon/core.c index 947486a150ce..28a2c78914fa 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -10,8 +10,12 @@ #include <linux/damon.h> #include <linux/delay.h> #include <linux/kthread.h> +#include <linux/random.h> #include <linux/slab.h>
+/* Get a random number in [l, r) */ +#define damon_rand(l, r) (l + prandom_u32_max(r - l)) + static DEFINE_MUTEX(damon_lock); static int nr_running_ctxs;
@@ -40,19 +44,23 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end) * Add a region between two other regions */ inline void damon_insert_region(struct damon_region *r, - struct damon_region *prev, struct damon_region *next) + struct damon_region *prev, struct damon_region *next, + struct damon_target *t) { __list_add(&r->list, &prev->list, &next->list); + t->nr_regions++; }
void damon_add_region(struct damon_region *r, struct damon_target *t) { list_add_tail(&r->list, &t->regions_list); + t->nr_regions++; }
-static void damon_del_region(struct damon_region *r) +static void damon_del_region(struct damon_region *r, struct damon_target *t) { list_del(&r->list); + t->nr_regions--; }
static void damon_free_region(struct damon_region *r) @@ -60,9 +68,9 @@ static void damon_free_region(struct damon_region *r) kfree(r); }
-void damon_destroy_region(struct damon_region *r) +void damon_destroy_region(struct damon_region *r, struct damon_target *t) { - damon_del_region(r); + damon_del_region(r, t); damon_free_region(r); }
@@ -80,6 +88,7 @@ struct damon_target *damon_new_target(unsigned long id) return NULL;
t->id = id; + t->nr_regions = 0; INIT_LIST_HEAD(&t->regions_list);
return t; @@ -87,7 +96,7 @@ struct damon_target *damon_new_target(unsigned long id)
void damon_add_target(struct damon_ctx *ctx, struct damon_target *t) { - list_add_tail(&t->list, &ctx->region_targets); + list_add_tail(&t->list, &ctx->adaptive_targets); }
static void damon_del_target(struct damon_target *t) @@ -110,6 +119,11 @@ void damon_destroy_target(struct damon_target *t) damon_free_target(t); }
+unsigned int damon_nr_regions(struct damon_target *t) +{ + return t->nr_regions; +} + struct damon_ctx *damon_new_ctx(void) { struct damon_ctx *ctx; @@ -127,7 +141,10 @@ struct damon_ctx *damon_new_ctx(void)
mutex_init(&ctx->kdamond_lock);
- INIT_LIST_HEAD(&ctx->region_targets); + ctx->min_nr_regions = 10; + ctx->max_nr_regions = 1000; + + INIT_LIST_HEAD(&ctx->adaptive_targets);
return ctx; } @@ -157,6 +174,8 @@ void damon_destroy_ctx(struct damon_ctx *ctx) * @sample_int: time interval between samplings * @aggr_int: time interval between aggregations * @primitive_upd_int: time interval between monitoring primitive updates + * @min_nr_reg: minimal number of regions + * @max_nr_reg: maximum number of regions * * This function should not be called while the kdamond is running. * Every time interval is in micro-seconds. @@ -164,15 +183,49 @@ void damon_destroy_ctx(struct damon_ctx *ctx) * Return: 0 on success, negative error code otherwise. */ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int, - unsigned long aggr_int, unsigned long primitive_upd_int) + unsigned long aggr_int, unsigned long primitive_upd_int, + unsigned long min_nr_reg, unsigned long max_nr_reg) { + if (min_nr_reg < 3) { + pr_err("min_nr_regions (%lu) must be at least 3\n", + min_nr_reg); + return -EINVAL; + } + if (min_nr_reg > max_nr_reg) { + pr_err("invalid nr_regions. min (%lu) > max (%lu)\n", + min_nr_reg, max_nr_reg); + return -EINVAL; + } + ctx->sample_interval = sample_int; ctx->aggr_interval = aggr_int; ctx->primitive_update_interval = primitive_upd_int; + ctx->min_nr_regions = min_nr_reg; + ctx->max_nr_regions = max_nr_reg;
return 0; }
+/* Returns the size upper limit for each monitoring region */ +static unsigned long damon_region_sz_limit(struct damon_ctx *ctx) +{ + struct damon_target *t; + struct damon_region *r; + unsigned long sz = 0; + + damon_for_each_target(t, ctx) { + damon_for_each_region(r, t) + sz += r->ar.end - r->ar.start; + } + + if (ctx->min_nr_regions) + sz /= ctx->min_nr_regions; + if (sz < DAMON_MIN_REGION) + sz = DAMON_MIN_REGION; + + return sz; +} + static bool damon_kdamond_running(struct damon_ctx *ctx) { bool running; @@ -339,6 +392,150 @@ static void kdamond_reset_aggregated(struct damon_ctx *c) } }
+#define sz_damon_region(r) (r->ar.end - r->ar.start) + +/* + * Merge two adjacent regions into one region + */ +static void damon_merge_two_regions(struct damon_target *t, + struct damon_region *l, struct damon_region *r) +{ + unsigned long sz_l = sz_damon_region(l), sz_r = sz_damon_region(r); + + l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) / + (sz_l + sz_r); + l->ar.end = r->ar.end; + damon_destroy_region(r, t); +} + +#define diff_of(a, b) (a > b ? a - b : b - a) + +/* + * Merge adjacent regions having similar access frequencies + * + * t target affected by this merge operation + * thres '->nr_accesses' diff threshold for the merge + * sz_limit size upper limit of each region + */ +static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, + unsigned long sz_limit) +{ + struct damon_region *r, *prev = NULL, *next; + + damon_for_each_region_safe(r, next, t) { + if (prev && prev->ar.end == r->ar.start && + diff_of(prev->nr_accesses, r->nr_accesses) <= thres && + sz_damon_region(prev) + sz_damon_region(r) <= sz_limit) + damon_merge_two_regions(t, prev, r); + else + prev = r; + } +} + +/* + * Merge adjacent regions having similar access frequencies + * + * threshold '->nr_accesses' diff threshold for the merge + * sz_limit size upper limit of each region + * + * This function merges monitoring target regions which are adjacent and their + * access frequencies are similar. This is for minimizing the monitoring + * overhead under the dynamically changeable access pattern. If a merge was + * unnecessarily made, later 'kdamond_split_regions()' will revert it. + */ +static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold, + unsigned long sz_limit) +{ + struct damon_target *t; + + damon_for_each_target(t, c) + damon_merge_regions_of(t, threshold, sz_limit); +} + +/* + * Split a region in two + * + * r the region to be split + * sz_r size of the first sub-region that will be made + */ +static void damon_split_region_at(struct damon_ctx *ctx, + struct damon_target *t, struct damon_region *r, + unsigned long sz_r) +{ + struct damon_region *new; + + new = damon_new_region(r->ar.start + sz_r, r->ar.end); + if (!new) + return; + + r->ar.end = new->ar.start; + + damon_insert_region(new, r, damon_next_region(r), t); +} + +/* Split every region in the given target into 'nr_subs' regions */ +static void damon_split_regions_of(struct damon_ctx *ctx, + struct damon_target *t, int nr_subs) +{ + struct damon_region *r, *next; + unsigned long sz_region, sz_sub = 0; + int i; + + damon_for_each_region_safe(r, next, t) { + sz_region = r->ar.end - r->ar.start; + + for (i = 0; i < nr_subs - 1 && + sz_region > 2 * DAMON_MIN_REGION; i++) { + /* + * Randomly select size of left sub-region to be at + * least 10 percent and at most 90% of original region + */ + sz_sub = ALIGN_DOWN(damon_rand(1, 10) * + sz_region / 10, DAMON_MIN_REGION); + /* Do not allow blank region */ + if (sz_sub == 0 || sz_sub >= sz_region) + continue; + + damon_split_region_at(ctx, t, r, sz_sub); + sz_region = sz_sub; + } + } +} + +/* + * Split every target region into randomly-sized small regions + * + * This function splits every target region into random-sized small regions if + * current total number of the regions is equal or smaller than half of the + * user-specified maximum number of regions. This is for maximizing the + * monitoring accuracy under the dynamically changeable access patterns. If a + * split was unnecessarily made, later 'kdamond_merge_regions()' will revert + * it. + */ +static void kdamond_split_regions(struct damon_ctx *ctx) +{ + struct damon_target *t; + unsigned int nr_regions = 0; + static unsigned int last_nr_regions; + int nr_subregions = 2; + + damon_for_each_target(t, ctx) + nr_regions += damon_nr_regions(t); + + if (nr_regions > ctx->max_nr_regions / 2) + return; + + /* Maybe the middle of the region has different access frequency */ + if (last_nr_regions == nr_regions && + nr_regions < ctx->max_nr_regions / 3) + nr_subregions = 3; + + damon_for_each_target(t, ctx) + damon_split_regions_of(ctx, t, nr_subregions); + + last_nr_regions = nr_regions; +} + /* * Check whether it is time to check and apply the target monitoring regions * @@ -395,6 +592,8 @@ static int kdamond_fn(void *data) struct damon_ctx *ctx = (struct damon_ctx *)data; struct damon_target *t; struct damon_region *r, *next; + unsigned int max_nr_accesses = 0; + unsigned long sz_limit = 0;
mutex_lock(&ctx->kdamond_lock); pr_info("kdamond (%d) starts\n", ctx->kdamond->pid); @@ -405,6 +604,8 @@ static int kdamond_fn(void *data) if (ctx->callback.before_start && ctx->callback.before_start(ctx)) set_kdamond_stop(ctx);
+ sz_limit = damon_region_sz_limit(ctx); + while (!kdamond_need_stop(ctx)) { if (ctx->primitive.prepare_access_checks) ctx->primitive.prepare_access_checks(ctx); @@ -415,13 +616,17 @@ static int kdamond_fn(void *data) usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
if (ctx->primitive.check_accesses) - ctx->primitive.check_accesses(ctx); + max_nr_accesses = ctx->primitive.check_accesses(ctx);
if (kdamond_aggregate_interval_passed(ctx)) { + kdamond_merge_regions(ctx, + max_nr_accesses / 10, + sz_limit); if (ctx->callback.after_aggregation && ctx->callback.after_aggregation(ctx)) set_kdamond_stop(ctx); kdamond_reset_aggregated(ctx); + kdamond_split_regions(ctx); if (ctx->primitive.reset_aggregated) ctx->primitive.reset_aggregated(ctx); } @@ -429,11 +634,12 @@ static int kdamond_fn(void *data) if (kdamond_need_update_primitive(ctx)) { if (ctx->primitive.update) ctx->primitive.update(ctx); + sz_limit = damon_region_sz_limit(ctx); } } damon_for_each_target(t, ctx) { damon_for_each_region_safe(r, next, t) - damon_destroy_region(r); + damon_destroy_region(r, t); }
if (ctx->callback.before_terminate &&