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mm/damon/core: handle unreset probe_hits in probe_hits_mvsum()

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If damon_update_monitoring_result() is called at the end of the
aggregation interval, probe_hits is not reset.  That's because the value
will be exposed to the user via damon_region_aggregated trace event.

Meanwhile, damon_probe_hits_mvsum() can be called in this state.  Due to
its logic, it will return a value that is incorrectly high.  This could
happen if the user requested DAMOS schemes applied regions sysfs files
update exactly in the time sequence.

The impact is minor, but better to avoid.  Check the timing and simply
return the fully aggregated last_probe_hits, like
damon_nr_accesses_mvsum() also does.  It is not 100% accurate since it is
the last interval's aggregation.  But better than the value that is
completely reset.

Link: https://lore.kernel.org/20260708135359.122587-8-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SJ Park
2026-07-08 06:53:57 -07:00
committed by Andrew Morton
parent e06b7f0cf8
commit d59bf2653c
1 changed files with 3 additions and 0 deletions
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3
mm/damon/core.c
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@@ -290,6 +290,9 @@ unsigned char damon_probe_hits_mvsum(int probe_idx, struct damon_region *r,
ctx->passed_sample_intervals;
left_window_bp = mult_frac(left_window, 10000, window_len);
if (left_window_bp == 10000)
return r->last_probe_hits[probe_idx];
return damon_mvsum(r->probe_hits[probe_idx],
r->last_probe_hits[probe_idx], left_window_bp);
}