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Thu, 08 Oct 2026 03:44:57 -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 2/2] mm/damon/core: Copy only installed probe in damon_split_region_at() Date: Thu, 8 Oct 2026 18:44:45 +0800 Message-ID: <20261008104511.5290-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261007154851.45368-3-suhaas@s-joshi.in> References: <20261007154851.45368-3-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 On Wed, 07 Oct 2026 21:18:46 +0530 Suhaas Joshi wrote: > In damon_split_region_at(), we copy the entire probe_hits[] and > last_probe_hits[] arrays of DAMON_MAX_PROBES size. However it is possible > that the number of probes installed is less than DAMON_MAX_PROBES, in which > case one or more iterations is/are redundant. To remedy this, iterate over > only as many times as the number of installed probes. To do so, accept a > struct damon_ctx pointer in damon_split_region_at(), and update all > invocations of the function to pass the new argument. > > Also update damon_test_split_at() and damos_test_filter_out() in > core-kunit.h to supply a context to function paths that call > damon_split_region_at(). > > Signed-off-by: Suhaas Joshi > --- > mm/damon/core.c | 42 +++++++++++++++++--------------- > mm/damon/tests/core-kunit.h | 48 ++++++++++++++++++++++++++++++------- > 2 files changed, 63 insertions(+), 27 deletions(-) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index a3af5ee685e1..025df4d19e20 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -2049,8 +2049,8 @@ static unsigned long damon_region_sz_limit(struct damon_ctx *ctx) > return sz; > } > > -static int damon_split_region_at(struct damon_target *t, > - struct damon_region *r, unsigned long sz_r); > +static int damon_split_region_at(struct damon_ctx *ctx, struct damon_target *t, > + struct damon_region *r, unsigned long sz_r); > > /* > * damon_apply_min_nr_regions() - Make effect of min_nr_regions parameter. > @@ -2075,7 +2075,7 @@ static unsigned long damon_apply_min_nr_regions(struct damon_ctx *ctx) > damon_for_each_target(t, ctx) { > damon_for_each_region_safe(r, next, t) { > while (damon_sz_region(r) > max_region_sz) { > - if (damon_split_region_at(t, r, max_region_sz)) > + if (damon_split_region_at(ctx, t, r, max_region_sz)) > goto out; > r = damon_next_region(r); > } > @@ -2494,9 +2494,9 @@ static bool damos_valid_target(struct damon_ctx *c, struct damon_region *r, > * > * Return: true if the region should be skipped, false otherwise. > */ > -static bool damos_skip_charged_region(struct damon_target *t, > - struct damon_region *r, struct damos *s, > - unsigned long min_region_sz) > +static bool damos_skip_charged_region(struct damon_ctx *ctx, struct damon_target *t, > + struct damon_region *r, struct damos *s, > + unsigned long min_region_sz) > { > struct damos_quota *quota = &s->quota; > unsigned long sz_to_skip; > @@ -2523,7 +2523,7 @@ static bool damos_skip_charged_region(struct damon_target *t, > } > sz_to_skip = min_region_sz; > } > - damon_split_region_at(t, r, sz_to_skip); > + damon_split_region_at(ctx, t, r, sz_to_skip); > skip = true; > } > } > @@ -2581,12 +2581,12 @@ static bool damos_filter_match(struct damon_ctx *ctx, struct damon_target *t, > } > /* start before the range and overlap */ > if (r->ar.start < start) { > - damon_split_region_at(t, r, start - r->ar.start); > + damon_split_region_at(ctx, t, r, start - r->ar.start); > matched = false; > break; > } > /* start inside the range */ > - damon_split_region_at(t, r, end - r->ar.start); > + damon_split_region_at(ctx, t, r, end - r->ar.start); > matched = true; > break; > case DAMOS_FILTER_TYPE_PROBE_HITS_WSUM: > @@ -2779,7 +2779,7 @@ static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t, > c->min_region_sz); > if (!sz) > goto update_stat; > - if (damon_split_region_at(t, r, sz)) > + if (damon_split_region_at(c, t, r, sz)) > goto update_stat; > } > if (damos_core_filter_out(c, t, r, s)) > @@ -2826,7 +2826,7 @@ static void damon_do_apply_schemes(struct damon_ctx *c, > if (damos_quota_is_full(quota, c->min_region_sz)) > continue; > > - if (damos_skip_charged_region(t, r, s, c->min_region_sz)) > + if (damos_skip_charged_region(c, t, r, s, c->min_region_sz)) > continue; > > if (s->max_nr_snapshots && > @@ -3643,10 +3643,12 @@ static void damon_verify_split_region_at(struct damon_region *r, > * > * Return: 0 on success, negative error code otherwise. > */ > -static int damon_split_region_at(struct damon_target *t, > - struct damon_region *r, unsigned long sz_r) > +static int damon_split_region_at(struct damon_ctx *ctx, struct damon_target *t, > + struct damon_region *r, unsigned long sz_r) > { > struct damon_region *new; > + struct damon_probe *p; > + int i; > > damon_verify_split_region_at(r, sz_r); > new = damon_new_region(r->ar.start + sz_r, r->ar.end); > @@ -3658,11 +3660,13 @@ static int damon_split_region_at(struct damon_target *t, > new->age = r->age; > new->last_nr_accesses = r->last_nr_accesses; > new->nr_accesses = r->nr_accesses; > - /* todo: do this for only installed probes */ > - memcpy(new->probe_hits, r->probe_hits, sizeof(r->probe_hits)); > - memcpy(new->last_probe_hits, r->last_probe_hits, > - sizeof(r->last_probe_hits)); > > + i = 0; > + damon_for_each_probe(p, ctx) { > + new->probe_hits[i] = r->probe_hits[i]; > + new->last_probe_hits[i] = r->last_probe_hits[i]; > + ++i; > + } > damon_insert_region(new, r, damon_next_region(r), t); > return 0; > } > @@ -3691,7 +3695,7 @@ static void damon_split_regions_of(struct damon_ctx *ctx, > if (sz_sub == 0 || sz_sub >= sz_region) > continue; > > - damon_split_region_at(t, r, sz_sub); > + damon_split_region_at(ctx, t, r, sz_sub); > sz_region = sz_sub; > } > } > @@ -3723,7 +3727,7 @@ static void damon_split_some_regions(struct damon_ctx *ctx, > if (sz_sub == 0 || sz_sub >= sz_region) > continue; > > - damon_split_region_at(t, r, sz_sub); > + damon_split_region_at(ctx, t, r, sz_sub); > } > } > } > diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h > index 5ad89c1d9fc2..e02604c7e0bc 100644 > --- a/mm/damon/tests/core-kunit.h > +++ b/mm/damon/tests/core-kunit.h > @@ -141,12 +141,26 @@ static void damon_test_split_at(struct kunit *test) > { > struct damon_target *t; > struct damon_region *r, *r_new; > + struct damon_ctx *ctx; > + struct damon_probe *p; > > + 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"); > } > @@ -156,7 +170,7 @@ static void damon_test_split_at(struct kunit *test) > r->last_probe_hits[0] = 3; > r->age = 10; > damon_add_region(r, t); > - damon_split_region_at(t, r, 25); > + damon_split_region_at(ctx, t, r, 25); > KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2); > if (damon_nr_regions(t) != 2) > goto out; > @@ -176,6 +190,7 @@ static void damon_test_split_at(struct kunit *test) > > out: > damon_free_target(t); > + damon_destroy_ctx(ctx); > } > > static void damon_test_merge_two(struct kunit *test) > @@ -1648,19 +1663,35 @@ static void damos_test_filter_out(struct kunit *test) > struct damon_target *t; > struct damon_region *r, *r2; > struct damos_filter *f; > + struct damon_ctx *ctx; > + struct damon_probe *p; > + > + 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); > > f = damos_new_filter(DAMOS_FILTER_TYPE_ADDR, true, false); > - if (!f) > + if (!f) { > + damon_destroy_ctx(ctx); > kunit_skip(test, "filter alloc fail"); > + } > f->addr_range = (struct damon_addr_range){.start = 2, .end = 6}; > > t = damon_new_target(); > if (!t) { > + damon_destroy_ctx(ctx); > damos_destroy_filter(f); > kunit_skip(test, "target alloc fail"); > } > r = damon_new_region(3, 5); > if (!r) { > + damon_destroy_ctx(ctx); > damos_destroy_filter(f); > damon_free_target(t); > kunit_skip(test, "region alloc fail"); > @@ -1668,27 +1699,27 @@ static void damos_test_filter_out(struct kunit *test) > damon_add_region(r, t); > > /* region in the range */ > - KUNIT_EXPECT_TRUE(test, damos_filter_match(NULL, t, r, f, 1)); > + KUNIT_EXPECT_TRUE(test, damos_filter_match(ctx, t, r, f, 1)); > KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); > > /* region before the range */ > r->ar.start = 1; > r->ar.end = 2; > KUNIT_EXPECT_FALSE(test, > - damos_filter_match(NULL, t, r, f, 1)); > + damos_filter_match(ctx, t, r, f, 1)); > KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); > > /* region after the range */ > r->ar.start = 6; > r->ar.end = 8; > KUNIT_EXPECT_FALSE(test, > - damos_filter_match(NULL, t, r, f, 1)); > + damos_filter_match(ctx, t, r, f, 1)); > KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1); > > /* region started before the range */ > r->ar.start = 1; > r->ar.end = 4; > - KUNIT_EXPECT_FALSE(test, damos_filter_match(NULL, t, r, f, 1)); > + KUNIT_EXPECT_FALSE(test, damos_filter_match(ctx, t, r, f, 1)); > /* filter should have split the region */ > KUNIT_EXPECT_EQ(test, r->ar.start, 1); > KUNIT_EXPECT_EQ(test, r->ar.end, 2); > @@ -1704,7 +1735,7 @@ static void damos_test_filter_out(struct kunit *test) > r->ar.start = 2; > r->ar.end = 8; > KUNIT_EXPECT_TRUE(test, > - damos_filter_match(NULL, t, r, f, 1)); > + damos_filter_match(ctx, t, r, f, 1)); > /* filter should have split the region */ > KUNIT_EXPECT_EQ(test, r->ar.start, 2); > KUNIT_EXPECT_EQ(test, r->ar.end, 6); > @@ -1717,6 +1748,7 @@ static void damos_test_filter_out(struct kunit *test) > damon_destroy_region(r2, t); > > out: > + damon_destroy_ctx(ctx); > damon_free_target(t); > damos_free_filter(f); > } > -- > 2.55.0 Thank you for your patches! LGTM. Reviewed-by: Liew Rui Yan Best regards, Rui Yan