diff options
| -rw-r--r-- | include/linux/damon.h | 2 | ||||
| -rw-r--r-- | mm/damon/core.c | 40 |
2 files changed, 42 insertions, 0 deletions
diff --git a/include/linux/damon.h b/include/linux/damon.h index 17c504d236b9..487a545a11b4 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -622,6 +622,8 @@ void damon_add_region(struct damon_region *r, struct damon_target *t); void damon_destroy_region(struct damon_region *r, struct damon_target *t); int damon_set_regions(struct damon_target *t, struct damon_addr_range *ranges, unsigned int nr_ranges); +unsigned int damon_moving_sum(unsigned int mvsum, unsigned int nomvsum, + unsigned int len_window, unsigned int new_value); void damon_update_region_access_rate(struct damon_region *r, bool accessed); struct damos_filter *damos_new_filter(enum damos_filter_type type, diff --git a/mm/damon/core.c b/mm/damon/core.c index 10532159323a..b005dc15009f 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1549,6 +1549,46 @@ int damon_set_region_biggest_system_ram_default(struct damon_target *t, return damon_set_regions(t, &addr_range, 1); } +/* + * damon_moving_sum() - Calculate an inferred moving sum value. + * @mvsum: Inferred sum of the last @len_window values. + * @nomvsum: Non-moving sum of the last discrete @len_window window values. + * @len_window: The number of last values to take care of. + * @new_value: New value that will be added to the pseudo moving sum. + * + * Moving sum (moving average * window size) is good for handling noise, but + * the cost of keeping past values can be high for arbitrary window size. This + * function implements a lightweight pseudo moving sum function that doesn't + * keep the past window values. + * + * It simply assumes there was no noise in the past, and get the no-noise + * assumed past value to drop from @nomvsum and @len_window. @nomvsum is a + * non-moving sum of the last window. For example, if @len_window is 10 and we + * have 25 values, @nomvsum is the sum of the 11th to 20th values of the 25 + * values. Hence, this function simply drops @nomvsum / @len_window from + * given @mvsum and add @new_value. + * + * For example, if @len_window is 10 and @nomvsum is 50, the last 10 values for + * the last window could be vary, e.g., 0, 10, 0, 10, 0, 10, 0, 0, 0, 20. For + * calculating next moving sum with a new value, we should drop 0 from 50 and + * add the new value. However, this function assumes it got value 5 for each + * of the last ten times. Based on the assumption, when the next value is + * measured, it drops the assumed past value, 5 from the current sum, and add + * the new value to get the updated pseduo-moving average. + * + * This means the value could have errors, but the errors will be disappeared + * for every @len_window aligned calls. For example, if @len_window is 10, the + * pseudo moving sum with 11th value to 19th value would have an error. But + * the sum with 20th value will not have the error. + * + * Return: Pseudo-moving average after getting the @new_value. + */ +unsigned int damon_moving_sum(unsigned int mvsum, unsigned int nomvsum, + unsigned int len_window, unsigned int new_value) +{ + return mvsum - nomvsum / len_window + new_value; +} + /** * damon_update_region_access_rate() - Update the access rate of a region. * @r: The DAMON region to update for its access check result. |