mm/damon/schemes: account how many times quota limit has exceeded

If the time/space quotas of a given DAMON-based operation scheme is too
small, the scheme could show unexpectedly slow progress.  However, there
is no good way to notice the case in runtime.  This commit extends the
DAMOS stat to provide how many times the quota limits exceeded so that
the users can easily notice the case and tune the scheme.

Link: https://lkml.kernel.org/r/20211210150016.35349-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/damon.h b/include/linux/damon.h
index e0ad3d9aaeedbe44f684c1d8c2ac7120e5a740f8..af648388e7596bed662bcefb7a816c4699192170 100644 (file)
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -198,12 +198,14 @@ struct damos_watermarks {
  * @sz_tried:  Total size of regions that the scheme is tried to be applied.
  * @nr_applied:        Total number of regions that the scheme is applied.
  * @sz_applied:        Total size of regions that the scheme is applied.
+ * @qt_exceeds: Total number of times the quota of the scheme has exceeded.
  */
 struct damos_stat {
        unsigned long nr_tried;
        unsigned long sz_tried;
        unsigned long nr_applied;
        unsigned long sz_applied;
+       unsigned long qt_exceeds;
 };
 
 /**

diff --git a/mm/damon/core.c b/mm/damon/core.c
index d745bf28509ffa109cbc367eced38fdb48b304e9..d5120b326e1b6c0d30078790cd2518f13e85de7e 100644 (file)
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -693,6 +693,8 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
                if (time_after_eq(jiffies, quota->charged_from +
                                        msecs_to_jiffies(
                                                quota->reset_interval))) {
+                       if (quota->esz && quota->charged_sz >= quota->esz)
+                               s->stat.qt_exceeds++;
                        quota->total_charged_sz += quota->charged_sz;
                        quota->charged_from = jiffies;
                        quota->charged_sz = 0;