diff options
| -rw-r--r-- | include/linux/damon.h | 20 | ||||
| -rw-r--r-- | mm/damon/core.c | 68 |
2 files changed, 79 insertions, 9 deletions
diff --git a/include/linux/damon.h b/include/linux/damon.h index ab2f17d9926b..aa34ab433bc5 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -136,6 +136,9 @@ enum damos_action { * @weight_nr_accesses: Weight of the region's nr_accesses for prioritization. * @weight_age: Weight of the region's age for prioritization. * + * @get_score: Feedback function for self-tuning quota. + * @get_score_arg: Parameter for @get_score + * * To avoid consuming too much CPU time or IO resources for applying the * &struct damos->action to large memory, DAMON allows users to set time and/or * size quotas. The quotas can be set by writing non-zero values to &ms and @@ -153,6 +156,17 @@ enum damos_action { * You could customize the prioritization logic by setting &weight_sz, * &weight_nr_accesses, and &weight_age, because monitoring operations are * encouraged to respect those. + * + * If @get_score function pointer is set, DAMON calls it back with + * @get_score_arg and get the return value of it for every @reset_interval. + * Then, DAMON adjusts the effective quota using the return value as a feedback + * score to the current quota, using its internal feedback loop algorithm. + * + * The feedback loop algorithem assumes the quota input and the feedback score + * output are in a positive proportional relationship, and the goal of the + * tuning is getting the feedback screo value of 10,000. If @ms and/or @sz are + * set together, those work as a hard limit quota. If neither @ms nor @sz are + * set, the mechanism starts from the quota of one byte. */ struct damos_quota { unsigned long ms; @@ -163,6 +177,9 @@ struct damos_quota { unsigned int weight_nr_accesses; unsigned int weight_age; + unsigned long (*get_score)(void *arg); + void *get_score_arg; + /* private: */ /* For throughput estimation */ unsigned long total_charged_sz; @@ -179,6 +196,9 @@ struct damos_quota { /* For prioritization */ unsigned long histogram[DAMOS_MAX_SCORE + 1]; unsigned int min_score; + + /* For feedback loop */ + unsigned long esz_bp; }; /** diff --git a/mm/damon/core.c b/mm/damon/core.c index ce1562783e7e..f91715a58dc7 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1038,26 +1038,76 @@ static void damon_do_apply_schemes(struct damon_ctx *c, } } -/* Shouldn't be called if quota->ms and quota->sz are zero */ +/* + * damon_feed_loop_next_input() - get next input to achieve a target score. + * @last_input The last input. + * @score Current score that made with @last_input. + * + * Calculate next input to achieve the target score, based on the last input + * and current score. Assuming the input and the score are positively + * proportional, calculate how much compensation should be added to or + * subtracted from the last input as a proportion of the last input. Avoid + * next input always being zero by setting it non-zero always. In short form + * (assuming support of float and signed calculations), the algorithm is as + * below. + * + * next_input = max(last_input * ((goal - current) / goal + 1), 1) + * + * For simple implementation, we assume the target score is always 10,000. The + * caller should adjust @score for this. + * + * Returns next input that assumed to achieve the target score. + */ +static unsigned long damon_feed_loop_next_input(unsigned long last_input, + unsigned long score) +{ + const unsigned long goal = 10000; + unsigned long score_goal_diff = max(goal, score) - min(goal, score); + unsigned long score_goal_diff_bp = score_goal_diff * 10000 / goal; + unsigned long compensation = last_input * score_goal_diff_bp / 10000; + /* Set minimum input as 10000 to avoid compensation be zero */ + const unsigned long min_input = 10000; + + if (goal > score) + return last_input + compensation; + if (last_input > compensation + min_input) + return last_input - compensation; + return min_input; +} + +/* Shouldn't be called if quota->ms, quota->sz, and quota->get_score unset */ static void damos_set_effective_quota(struct damos_quota *quota) { unsigned long throughput; unsigned long esz; - if (!quota->ms) { + if (!quota->ms && !quota->get_score) { quota->esz = quota->sz; return; } - if (quota->total_charged_ns) - throughput = quota->total_charged_sz * 1000000 / - quota->total_charged_ns; - else - throughput = PAGE_SIZE * 1024; - esz = throughput * quota->ms; + if (quota->get_score) { + quota->esz_bp = damon_feed_loop_next_input( + max(quota->esz_bp, 10000UL), + quota->get_score(quota->get_score_arg)); + esz = quota->esz_bp / 10000; + } + + if (quota->ms) { + if (quota->total_charged_ns) + throughput = quota->total_charged_sz * 1000000 / + quota->total_charged_ns; + else + throughput = PAGE_SIZE * 1024; + if (quota->get_score) + esz = min(throughput * quota->ms, esz); + else + esz = throughput * quota->ms; + } if (quota->sz && quota->sz < esz) esz = quota->sz; + quota->esz = esz; } @@ -1069,7 +1119,7 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) unsigned long cumulated_sz; unsigned int score, max_score = 0; - if (!quota->ms && !quota->sz) + if (!quota->ms && !quota->sz && !quota->get_score) return; /* New charge window starts */ |