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b=FnKATpWvDwkHRwdi9Uav1cD+mTAY2mfWw9x4neKuDXB+UkN3ME3GrN0aTqK3bnXKR UahrR9MatgNRQp8lcBKKxTCp44jVg6UdjIDyPWtNas6yFDl8E8PxfCUfrxyqg6s9z7 4X8JiaU0kCdrp+SZ3TrAGpCu+2iF8abRAx2swsglG/mCp5WCPmf+12o0cfJ4fdFx/d +jC4BdEwcAL3TT7V0mQ7tmXBTHXF6uNR60ZyLWS2jSYoYpCmQPGJgn8imLYKCvyYEc /SvhOqO1BtPJN0Kch5b3h9z1RyNM+fQzI9s2KDWPpOzDtK5l7dhIlUgooKIxv5y9FE Bjg4YrbyBTk/w== From: SeongJae Park To: Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.3 03/18] mm/damon/core: always update ->last_nr_accesses for intervals change Date: Mon, 22 Jun 2026 07:21:23 -0700 Message-ID: <20260622142139.30269-4-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260622142139.30269-1-sj@kernel.org> References: <20260622142139.30269-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: fed74tmkaukh5ugmfy7tskzn187dgzzd X-Rspamd-Queue-Id: 2793B140007 X-Rspamd-Server: rspam11 X-HE-Tag: 1782138110-575406 X-HE-Meta: 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 i/hlFUNJ EwXeGsGLeYRKHXe7OrUlgazKwOhLIbT0bHi0dSQT938G//0JfvgC6FpLlzvxramJj3kM4HnYFTzLK+BdVuDtSKpL+wFipnoAs4HBLaZYkLbSv7PRws2SDmG/iXrCre4aYkkRsohsCojauuIaRdHCemRvgg34ZLcQ6Jl2ZroWtYwowQ7kCFGTOB5SW5v0ODl5kT+wsvGAELaov3sl7tj6sc583qTzVUBu9DVFUF4EDTuyrBynHtWE400gT40gMTvzW5MKhGuBo9DX1AvJRx570SRC6cw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Each iteration of kdamond_fn() main loop caches and use the next aggregation time (next_aggregation_sis) because it can be updated in the middle, inside kdamond_call(). If that happens, damon_update_monitoring_result() is called for scaling the access frequency information of each region according to the changed intervals. The function does not update damon_region->last_nr_accesses when it is at the end of the aggregation, because it will anyway be reset after the function is executed, in kdamond_reset_aggregated(). Let's suppose damon_nr_accesses_mvsum() is called with the not yet updated last_nr_accesses. It will use the fresh next_aggregation_sis in the context instead of the cached one, unlike kdamond_fn(). As a result, use of not updated last_nr_acceses with the updated next_aggregation_sis result in returning wrong value. There is no such damon_nr_accesses_nvsum() call at the moment, so this is no problem. It is planned to add such calls, though. Prevent the issue by updating last_nr_accesses always. This adds overhead, but that's fine because the overhead is not big, and it is anyway not a fast path. Signed-off-by: SeongJae Park --- mm/damon/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 2cc911fa221aa..191533685cf2f 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -873,6 +873,8 @@ static void damon_update_monitoring_result(struct damon_region *r, struct damon_attrs *old_attrs, struct damon_attrs *new_attrs, bool aggregating) { + r->last_nr_accesses = damon_nr_accesses_for_new_attrs( + r->last_nr_accesses, old_attrs, new_attrs); if (!aggregating) { r->nr_accesses = damon_nr_accesses_for_new_attrs( r->nr_accesses, old_attrs, new_attrs); @@ -884,8 +886,6 @@ static void damon_update_monitoring_result(struct damon_region *r, * interval. In other words, make the status like * kdamond_reset_aggregated() is called. */ - r->last_nr_accesses = damon_nr_accesses_for_new_attrs( - r->last_nr_accesses, old_attrs, new_attrs); r->nr_accesses_bp = r->last_nr_accesses * 10000; r->nr_accesses = 0; } -- 2.47.3