selftests/damon/access_memory: use user-defined region size

Patch series "selftests/damon: test DAMOS tried regions and
{min,max}_nr_regions".

This patch series fix a minor issue in a program for DAMON selftest, and
implement new functionality selftests for DAMOS tried regions and
{min,max}_nr_regions.  The test for max_nr_regions also test the recovery
from online tuning-caused limit violation, which was fixed by a previous
patch [1] titled "mm/damon/core: merge regions aggressively when
max_nr_regions is unmet".

The first patch fixes a minor problem in the articial memory access
pattern generator for tests.  Following 3 patches (2-4) implement schemes
tried regions test.  Then a couple of patches (5-6) implementing static
setup based {min,max}_nr_regions functionality test follows.  Final two
patches (7-8) implement dynamic max_nr_regions update test.

[1] https://lore.kernel.org/20240624210650.53960C2BBFC@smtp.kernel.org


This patch (of 8):

'access_memory' is an artificial memory access pattern generator for DAMON
tests.  It creates and accesses memory regions that the user specified the
number and size via the command line.  However, real access part of the
program ignores the user-specified size of each region.  Instead, it uses
a hard-coded value, 10 MiB.  Fix it to use user-defined size.

Note that all existing 'access_memory' users are setting the region size
as 10 MiB.  Hence no real problem has happened so far.

Link: https://lkml.kernel.org/r/20240625180538.73134-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240625180538.73134-2-sj@kernel.org
Fixes: b5906f5f ("selftests/damon: add a test for update_schemes_tried_regions sysfs command")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/access_memory.c

@@ -35,7 +35,7 @@ int main(int argc, char *argv[])
 		start_clock = clock();
 		while ((clock() - start_clock) * 1000 / CLOCKS_PER_SEC <
 				access_time_ms)
-			memset(regions[i], i, 1024 * 1024 * 10);
+			memset(regions[i], i, sz_region);
 	}
 	return 0;
 }