Hardware integer division is slow. The function damon_max_nr_accesses(), which is called very frequently, performs an integer division. However, the struct damon_attrs already caches this exact ratio in the internal field aggr_samples. We can eliminate the hardware division in the hot path by simply returning aggr_samples. Signed-off-by: Josh Law --- include/linux/damon.h | 3 +-- mm/damon/core.c | 1 + mm/damon/tests/core-kunit.h | 16 ++++++++++++---- 3 files changed, 14 insertions(+), 6 deletions(-) diff --git a/include/linux/damon.h b/include/linux/damon.h index 6bd71546f7b2..438fe6f3eab4 100644 --- a/include/linux/damon.h +++ b/include/linux/damon.h @@ -960,8 +960,7 @@ static inline bool damon_target_has_pid(const struct damon_ctx *ctx) static inline unsigned int damon_max_nr_accesses(const struct damon_attrs *attrs) { /* {aggr,sample}_interval are unsigned long, hence could overflow */ - return min(attrs->aggr_interval / attrs->sample_interval, - (unsigned long)UINT_MAX); + return min_t(unsigned long, attrs->aggr_samples, UINT_MAX); } diff --git a/mm/damon/core.c b/mm/damon/core.c index b0ab0ee6eab9..59b709f04975 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -582,6 +582,7 @@ struct damon_ctx *damon_new_ctx(void) ctx->attrs.sample_interval = 5 * 1000; ctx->attrs.aggr_interval = 100 * 1000; ctx->attrs.ops_update_interval = 60 * 1000 * 1000; + ctx->attrs.aggr_samples = 20; ctx->passed_sample_intervals = 0; /* These will be set from kdamond_init_ctx() */ diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h index e86d4f4fe261..56d03ef6a5a4 100644 --- a/mm/damon/tests/core-kunit.h +++ b/mm/damon/tests/core-kunit.h @@ -416,6 +416,8 @@ static void damon_test_nr_accesses_to_accesses_bp(struct kunit *test) .aggr_interval = ((unsigned long)UINT_MAX + 1) * 10 }; + attrs.aggr_samples = attrs.aggr_interval / attrs.sample_interval; + /* * In some cases such as 32bit architectures where UINT_MAX is * ULONG_MAX, attrs.aggr_interval becomes zero. Calling @@ -434,7 +436,8 @@ static void damon_test_nr_accesses_to_accesses_bp(struct kunit *test) static void damon_test_update_monitoring_result(struct kunit *test) { struct damon_attrs old_attrs = { - .sample_interval = 10, .aggr_interval = 1000,}; + .sample_interval = 10, .aggr_interval = 1000, + .aggr_samples = 100,}; struct damon_attrs new_attrs; struct damon_region *r = damon_new_region(3, 7); @@ -446,19 +449,24 @@ static void damon_test_update_monitoring_result(struct kunit *test) r->age = 20; new_attrs = (struct damon_attrs){ - .sample_interval = 100, .aggr_interval = 10000,}; + .sample_interval = 100, .aggr_interval = 10000, + .aggr_samples = 100,}; damon_update_monitoring_result(r, &old_attrs, &new_attrs, false); KUNIT_EXPECT_EQ(test, r->nr_accesses, 15); KUNIT_EXPECT_EQ(test, r->age, 2); new_attrs = (struct damon_attrs){ - .sample_interval = 1, .aggr_interval = 1000}; + .sample_interval = 1, .aggr_interval = 1000, + .aggr_samples = 1000, + }; damon_update_monitoring_result(r, &old_attrs, &new_attrs, false); KUNIT_EXPECT_EQ(test, r->nr_accesses, 150); KUNIT_EXPECT_EQ(test, r->age, 2); new_attrs = (struct damon_attrs){ - .sample_interval = 1, .aggr_interval = 100}; + .sample_interval = 1, .aggr_interval = 100, + .aggr_samples = 100, + }; damon_update_monitoring_result(r, &old_attrs, &new_attrs, false); KUNIT_EXPECT_EQ(test, r->nr_accesses, 150); KUNIT_EXPECT_EQ(test, r->age, 20); -- 2.34.1