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mm/damon/core: handle unreset nr_accesses in damon_nr_accesses_mvsum()

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damon_set_attrs() works like reverting aggregations that were made so far
for this aggregation window.  If this is the end of the aggregation,
however, kdamond_fn() will do the operations at the end of the aggregation
interval, using cached timestamps.  For such operations that rely on
damon_region->nr_accesses, damon_update_monitoring_results() doesn't reset
the nr_accesses if it is called at the end of the aggregation window.

damon_nr_accesses_mvsum() works with fresh timestamps, though.  The
nr_accesses that are not reset in this case can make the logic to
unnecessarily count nr_accesses, resulting in returning
higher-than-expected pseudo moving sum nr_accesses.  No code is using
damon_nr_accesses_mvsum() yet, so this is not causing a real problem. 
Following commits will add usage of the function, though.  For safe
usages, calculate the pseudo moving sum without nr_accesses if the
remaining window is full.

Link: https://lore.kernel.org/20260630040812.149729-5-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SJ Park 2026-06-29 21:07:57 -07:00 committed by Andrew Morton
parent a44821c65c
commit 1b43501d68
1 changed files with 3 additions and 0 deletions
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mm/damon/core.c
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@ -266,6 +266,9 @@ unsigned int damon_nr_accesses_mvsum(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_nr_accesses;
return damon_mvsum(r->nr_accesses, r->last_nr_accesses,
left_window_bp);
}