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mm/damon/core: add damon_merge_regions_of() debug_sanity check

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damon_merge_regions_of() should be called only after aggregation is
finished and therefore each region's nr_accesses and nr_accesses_bp match.
There were bugs that broke the assumption, during development of online
DAMON parameter updates and monitoring results handling changes.  Add a
sanity check for that under CONFIG_DAMON_DEBUG_SANITY.

Link: https://lkml.kernel.org/r/20260306152914.86303-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SeongJae Park 2026-03-06 07:29:09 -08:00 committed by Andrew Morton
parent 0bb7682fdb
commit c070da2391
1 changed files with 15 additions and 0 deletions
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15
mm/damon/core.c
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@ -2507,6 +2507,20 @@ static void damon_merge_two_regions(struct damon_target *t,
damon_destroy_region(r, t);
}
#ifdef CONFIG_DAMON_DEBUG_SANITY
static void damon_verify_merge_regions_of(struct damon_region *r)
{
WARN_ONCE(r->nr_accesses != r->nr_accesses_bp / 10000,
"nr_accesses (%u) != nr_accesses_bp (%u)\n",
r->nr_accesses, r->nr_accesses_bp);
}
#else
static void damon_verify_merge_regions_of(struct damon_region *r)
{
}
#endif
/*
* Merge adjacent regions having similar access frequencies
*
@ -2520,6 +2534,7 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
struct damon_region *r, *prev = NULL, *next;
damon_for_each_region_safe(r, next, t) {
damon_verify_merge_regions_of(r);
if (abs(r->nr_accesses - r->last_nr_accesses) > thres)
r->age = 0;
else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0))