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Thu, 08 Oct 2026 03:40:57 -0700 (PDT) From: Liew Rui Yan To: suhaas@s-joshi.in Cc: Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, SJ Park , Liew Rui Yan Subject: [PATCH 1/2] mm/damon/core: Use only installed probe in damon_merge_two_regions() Date: Thu, 8 Oct 2026 18:40:29 +0800 Message-ID: <20261008104112.4763-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261007154851.45368-2-suhaas@s-joshi.in> References: <20261007154851.45368-2-suhaas@s-joshi.in> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Suhaas, Thank you for your patches series! On Wed, 07 Oct 2026 21:18:45 +0530 Suhaas Joshi wrote: > While merging 2 regions, we iterate over the entire probe_hits[] array, > whose size is determined by the DAMON_MAX_PROBES macro. It is possible, > however, that we have fewer probes installed than DAMON_MAX_PROBES. In such I find this a bit hard to read. Could we change it to this? "However, it is possible that we have fewer probes installed than DAMON_MAX_PROBES." > cases, we end up making redundant iterations. Therefore, to remedy this, > iterate over the list of installed probes instead of iterating over the > entire array. For doing this, start accepting a struct damon_ctx in > damon_merge_two_regions(), and update calling functions to pass this > argument. > > Update the damon_test_merge_two() test to use this new signature for > damon_merge_two_regions() as well. > > Signed-off-by: Suhaas Joshi > --- > mm/damon/core.c | 14 +++++++++----- > mm/damon/tests/core-kunit.h | 19 +++++++++++++++++-- > 2 files changed, 26 insertions(+), 7 deletions(-) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 733025b36745..a3af5ee685e1 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -3499,20 +3499,24 @@ static void damon_verify_merge_two_regions( > /* > * Merge two adjacent regions into one region > */ > -static void damon_merge_two_regions(struct damon_target *t, > - struct damon_region *l, struct damon_region *r) > +static void damon_merge_two_regions(struct damon_ctx *ctx, struct damon_target *t, > + struct damon_region *l, struct damon_region *r) > { > unsigned long sz_l = damon_sz_region(l), sz_r = damon_sz_region(r); > int i; > + struct damon_probe *p; > > l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) / > (sz_l + sz_r); > l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r); > l->ar.end = r->ar.end; > - /* todo: do this for only installed probes */ > - for (i = 0; i < DAMON_MAX_PROBES; i++) > + > + i = 0; > + damon_for_each_probe(p, ctx) { > l->probe_hits[i] = (l->probe_hits[i] * sz_l + r->probe_hits[i] > * sz_r) / (sz_l + sz_r); > + ++i; > + } > damon_verify_merge_two_regions(l, r); > damon_destroy_region(r, t); > } > @@ -3565,7 +3569,7 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, > goto set_prev_continue; > if (damon_sz_region(prev) + damon_sz_region(r) > sz_limit) > goto set_prev_continue; > - damon_merge_two_regions(t, prev, r); > + damon_merge_two_regions(ctx, t, prev, r); > continue; > set_prev_continue: > prev = r; > diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h > index df84d9cc7d20..5ad89c1d9fc2 100644 > --- a/mm/damon/tests/core-kunit.h > +++ b/mm/damon/tests/core-kunit.h > @@ -182,13 +182,27 @@ static void damon_test_merge_two(struct kunit *test) > { > struct damon_target *t; > struct damon_region *r, *r2, *r3; > + struct damon_probe *p; > + struct damon_ctx *ctx; > int i; > > + p = damon_new_probe(); > + if (!p) > + kunit_skip(test, "probe alloc fail"); > + ctx = damon_new_ctx(); > + if (!ctx) { > + damon_destroy_probe(p); > + kunit_skip(test, "context alloc fail"); > + } > + damon_add_probe(ctx, p); > t = damon_new_target(); > - if (!t) > + if (!t) { > + damon_destroy_ctx(ctx); > kunit_skip(test, "target alloc fail"); > + } > r = damon_new_region(0, 100); > if (!r) { > + damon_destroy_ctx(ctx); > damon_free_target(t); > kunit_skip(test, "region alloc fail"); > } > @@ -206,7 +220,7 @@ static void damon_test_merge_two(struct kunit *test) > r2->age = 21; > damon_add_region(r2, t); > > - damon_merge_two_regions(t, r, r2); > + damon_merge_two_regions(ctx, t, r, r2); > KUNIT_EXPECT_EQ(test, r->ar.start, 0ul); > KUNIT_EXPECT_EQ(test, r->ar.end, 300ul); > KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u); > @@ -220,6 +234,7 @@ static void damon_test_merge_two(struct kunit *test) > } > KUNIT_EXPECT_EQ(test, i, 1); > > + damon_destroy_ctx(ctx); > damon_free_target(t); > } > > -- > 2.55.0 Other than the commit message I just mentioned, and the issue reported [1] by Sashiko, LGTM. Reviewed-by: Liew Rui Yan [1] https://lore.kernel.org/damon/sashiko-outbox-163177@kernel.org Best regards, Rui Yan