SeongJae Park 1e865019ce mm/damon/core: merge regions aggressively when max_nr_regions is unmet ... commit 310d6c15e9 upstream. DAMON keeps the number of regions under max_nr_regions by skipping regions split operations when doing so can make the number higher than the limit. It works well for preventing violation of the limit. But, if somehow the violation happens, it cannot recovery well depending on the situation. In detail, if the real number of regions having different access pattern is higher than the limit, the mechanism cannot reduce the number below the limit. In such a case, the system could suffer from high monitoring overhead of DAMON. The violation can actually happen. For an example, the user could reduce max_nr_regions while DAMON is running, to be lower than the current number of regions. Fix the problem by repeating the merge operations with increasing aggressiveness in kdamond_merge_regions() for the case, until the limit is met. [sj@kernel.org: increase regions merge aggressiveness while respecting min_nr_regions] Link: https://lkml.kernel.org/r/20240626164753.46270-1-sj@kernel.org [sj@kernel.org: ensure max threshold attempt for max_nr_regions violation] Link: https://lkml.kernel.org/r/20240627163153.75969-1-sj@kernel.org Link: https://lkml.kernel.org/r/20240624175814.89611-1-sj@kernel.org Fixes: b9a6ac4e4e ("mm/damon: adaptively adjust regions") Signed-off-by: SeongJae Park <sj@kernel.org> Cc: <stable@vger.kernel.org> [5.15+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> (cherry picked from commit 310d6c15e9) Signed-off-by: SeongJae Park <sj@kernel.org> [Remove use of unexisting damon_ctx->attrs field] Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2024-07-27 10:46:15 +02:00
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core-test.h	mm/damon/core-test: fix wrong expectations for 'damon_split_regions_of()'	2021-10-28 17:18:55 -07:00
core.c	mm/damon/core: merge regions aggressively when max_nr_regions is unmet	2024-07-27 10:46:15 +02:00
dbgfs-test.h	mm/damon: don't use strnlen() with known-bogus source length	2021-09-24 16:13:34 -07:00
dbgfs.c	mm/damon/dbgfs: check if rm_contexts input is for a real context	2022-11-16 09:58:27 +01:00
Kconfig	mm/damon: add kunit tests	2021-09-08 11:50:25 -07:00
Makefile	mm/damon: implement a debugfs-based user space interface	2021-09-08 11:50:24 -07:00
vaddr-test.h	mm/damon: add kunit tests	2021-09-08 11:50:25 -07:00
vaddr.c	mm/damon/ops-common: atomically test and clear young on ptes and pmds	2023-07-23 13:47:47 +02:00