From f23b8eee1871a6db5c37f90831147de5426c40b7 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Tue, 7 Sep 2021 19:56:32 -0700 Subject: mm/damon/core: implement region-based sampling To avoid the unbounded increase of the overhead, DAMON groups adjacent pages that are assumed to have the same access frequencies into a region. As long as the assumption (pages in a region have the same access frequencies) is kept, only one page in the region is required to be checked. Thus, for each ``sampling interval``, 1. the 'prepare_access_checks' primitive picks one page in each region, 2. waits for one ``sampling interval``, 3. checks whether the page is accessed meanwhile, and 4. increases the access count of the region if so. Therefore, the monitoring overhead is controllable by adjusting the number of regions. DAMON allows both the underlying primitives and user callbacks to adjust regions for the trade-off. In other words, this commit makes DAMON to use not only time-based sampling but also space-based sampling. This scheme, however, cannot preserve the quality of the output if the assumption is not guaranteed. Next commit will address this problem. Link: https://lkml.kernel.org/r/20210716081449.22187-3-sj38.park@gmail.com Signed-off-by: SeongJae Park Reviewed-by: Leonard Foerster Reviewed-by: Fernand Sieber Acked-by: Shakeel Butt Cc: Alexander Shishkin Cc: Amit Shah Cc: Benjamin Herrenschmidt Cc: Brendan Higgins Cc: David Hildenbrand Cc: David Rientjes Cc: David Woodhouse Cc: Fan Du Cc: Greg Kroah-Hartman Cc: Greg Thelen Cc: Ingo Molnar Cc: Joe Perches Cc: Jonathan Cameron Cc: Jonathan Corbet Cc: Marco Elver Cc: Markus Boehme Cc: Maximilian Heyne Cc: Mel Gorman Cc: Minchan Kim Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Rik van Riel Cc: Shuah Khan Cc: Steven Rostedt (VMware) Cc: Vladimir Davydov Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/damon/core.c | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 139 insertions(+), 4 deletions(-) (limited to 'mm') diff --git a/mm/damon/core.c b/mm/damon/core.c index 651590bf49b1..947486a150ce 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -15,6 +15,101 @@ static DEFINE_MUTEX(damon_lock); static int nr_running_ctxs; +/* + * Construct a damon_region struct + * + * Returns the pointer to the new struct if success, or NULL otherwise + */ +struct damon_region *damon_new_region(unsigned long start, unsigned long end) +{ + struct damon_region *region; + + region = kmalloc(sizeof(*region), GFP_KERNEL); + if (!region) + return NULL; + + region->ar.start = start; + region->ar.end = end; + region->nr_accesses = 0; + INIT_LIST_HEAD(®ion->list); + + return region; +} + +/* + * Add a region between two other regions + */ +inline void damon_insert_region(struct damon_region *r, + struct damon_region *prev, struct damon_region *next) +{ + __list_add(&r->list, &prev->list, &next->list); +} + +void damon_add_region(struct damon_region *r, struct damon_target *t) +{ + list_add_tail(&r->list, &t->regions_list); +} + +static void damon_del_region(struct damon_region *r) +{ + list_del(&r->list); +} + +static void damon_free_region(struct damon_region *r) +{ + kfree(r); +} + +void damon_destroy_region(struct damon_region *r) +{ + damon_del_region(r); + damon_free_region(r); +} + +/* + * Construct a damon_target struct + * + * Returns the pointer to the new struct if success, or NULL otherwise + */ +struct damon_target *damon_new_target(unsigned long id) +{ + struct damon_target *t; + + t = kmalloc(sizeof(*t), GFP_KERNEL); + if (!t) + return NULL; + + t->id = id; + INIT_LIST_HEAD(&t->regions_list); + + return t; +} + +void damon_add_target(struct damon_ctx *ctx, struct damon_target *t) +{ + list_add_tail(&t->list, &ctx->region_targets); +} + +static void damon_del_target(struct damon_target *t) +{ + list_del(&t->list); +} + +void damon_free_target(struct damon_target *t) +{ + struct damon_region *r, *next; + + damon_for_each_region_safe(r, next, t) + damon_free_region(r); + kfree(t); +} + +void damon_destroy_target(struct damon_target *t) +{ + damon_del_target(t); + damon_free_target(t); +} + struct damon_ctx *damon_new_ctx(void) { struct damon_ctx *ctx; @@ -32,15 +127,27 @@ struct damon_ctx *damon_new_ctx(void) mutex_init(&ctx->kdamond_lock); - ctx->target = NULL; + INIT_LIST_HEAD(&ctx->region_targets); return ctx; } -void damon_destroy_ctx(struct damon_ctx *ctx) +static void damon_destroy_targets(struct damon_ctx *ctx) { - if (ctx->primitive.cleanup) + struct damon_target *t, *next_t; + + if (ctx->primitive.cleanup) { ctx->primitive.cleanup(ctx); + return; + } + + damon_for_each_target_safe(t, next_t, ctx) + damon_destroy_target(t); +} + +void damon_destroy_ctx(struct damon_ctx *ctx) +{ + damon_destroy_targets(ctx); kfree(ctx); } @@ -217,6 +324,21 @@ static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx) ctx->aggr_interval); } +/* + * Reset the aggregated monitoring results ('nr_accesses' of each region). + */ +static void kdamond_reset_aggregated(struct damon_ctx *c) +{ + struct damon_target *t; + + damon_for_each_target(t, c) { + struct damon_region *r; + + damon_for_each_region(r, t) + r->nr_accesses = 0; + } +} + /* * Check whether it is time to check and apply the target monitoring regions * @@ -238,6 +360,7 @@ static bool kdamond_need_update_primitive(struct damon_ctx *ctx) */ static bool kdamond_need_stop(struct damon_ctx *ctx) { + struct damon_target *t; bool stop; mutex_lock(&ctx->kdamond_lock); @@ -249,7 +372,12 @@ static bool kdamond_need_stop(struct damon_ctx *ctx) if (!ctx->primitive.target_valid) return false; - return !ctx->primitive.target_valid(ctx->target); + damon_for_each_target(t, ctx) { + if (ctx->primitive.target_valid(t)) + return false; + } + + return true; } static void set_kdamond_stop(struct damon_ctx *ctx) @@ -265,6 +393,8 @@ static void set_kdamond_stop(struct damon_ctx *ctx) static int kdamond_fn(void *data) { struct damon_ctx *ctx = (struct damon_ctx *)data; + struct damon_target *t; + struct damon_region *r, *next; mutex_lock(&ctx->kdamond_lock); pr_info("kdamond (%d) starts\n", ctx->kdamond->pid); @@ -291,6 +421,7 @@ static int kdamond_fn(void *data) if (ctx->callback.after_aggregation && ctx->callback.after_aggregation(ctx)) set_kdamond_stop(ctx); + kdamond_reset_aggregated(ctx); if (ctx->primitive.reset_aggregated) ctx->primitive.reset_aggregated(ctx); } @@ -300,6 +431,10 @@ static int kdamond_fn(void *data) ctx->primitive.update(ctx); } } + damon_for_each_target(t, ctx) { + damon_for_each_region_safe(r, next, t) + damon_destroy_region(r); + } if (ctx->callback.before_terminate && ctx->callback.before_terminate(ctx)) -- cgit v1.2.3-58-ga151