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b=gwklBata4izVqdnVUPTJdgYIIsv8m03v60Hc+bMKD8+zpMaEnf8Yh8YDnirz6DcnS L/+gLFuj1V1AQSivhZN/XcFQkIJlA7VweNG1lchxo0slVwPTtkhHlcKKwCj2pxSf1B w5eLrgV2SK/isxSwfgEyYXEDeaXK0EMaPeguxTCYGPh+x4orL86omnezAdibluxnzZ 0/eIHOmCJYta0REGuZ54YSkc26p7OVIWdEK/3U8lY1txZXIvADbR+Eam7vnVuYK7P+ hM53XYqQzBD43q0DgRgeVSkSu4wrs4tWgEWrrscS7pVK6ZwmLPf7gO87jtiYekszij u2/FKsV2OMNtw== From: SJ Park To: Suhaas Joshi Cc: SJ Park , akpm@linux-foundation.org, aethernet65535@gmail.com, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] mm/damon/core: Use only installed probe in damon_merge_two_regions() Date: Fri, 9 Oct 2026 00:43:49 -0700 Message-ID: <20261009074349.40812-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261008151944.113714-2-suhaas@s-joshi.in> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 2F893180009 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: uiowzrp4eyityhzjth8eyhhfpcqzocd5 X-HE-Tag: 1791531837-130117 X-HE-Meta: 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 fqI14nrZ tUcabdeHFjvdu/FzgtHjtY09JgWpvHyAMBlEZwQx4tzsK2aPRvCZt44vSWV051X858GoteITAyBNGmNcvuSTCA2muwbB7r0+51P7qqriXZkVjGzpIowcNc4GxcUVEgVTKpWICSOSAf2fuSXsz05Lt+k0tiynsrqAaCjZExtF8Tf7tQo7c3Z5k3ZcsXIPlowNVZq6+aY6alwe+5UMKtN0pjTLXanXzRMAziCFCVwxHeh++ojA5YW+HSif0D3m3TUNTvSrA Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Suhaas, On Thu, 8 Oct 2026 20:49:25 +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. However, it is > possible that we have fewer probes installed than DAMON_MAX_PROBES. In such > 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 | 16 +++++++++++----- > mm/damon/tests/core-kunit.h | 20 ++++++++++++++++++-- > 2 files changed, 29 insertions(+), 7 deletions(-) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index b63e60ef8990..fc202f90991b 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -3524,20 +3524,26 @@ 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) Please use two tabs for indentation of the second and next lines of function parameters. For example: ''' @@ -3739,8 +3739,9 @@ static noinline_for_stack void kdamond_apply_schemes(struct damon_ctx *c) } #ifdef CONFIG_DAMON_DEBUG_SANITY -static void damon_verify_merge_two_regions( - struct damon_region *l, struct damon_region *r) +static void damon_verify_merge_two_regions(struct damon_ctx *ctx, + struct damon_target *t, struct damon_region *l, + struct damon_region *r) { /* damon_merge_two_regions() may created incorrect left region */ WARN_ONCE(l->ar.start >= l->ar.end, "l: %lu-%lu, r: %lu-%lu\n", ''' > { > 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); > } > @@ -3590,7 +3596,7 @@ 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 ef146ca2ae8a..4e380c6c5eb2 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"); > } > @@ -198,6 +212,7 @@ static void damon_test_merge_two(struct kunit *test) > damon_add_region(r, t); > r2 = damon_new_region(100, 300); > if (!r2) { > + damon_destroy_ctx(ctx); > damon_free_target(t); > kunit_skip(test, "second region alloc fail"); > } > @@ -206,7 +221,7 @@ static void damon_test_merge_two(struct kunit *test) > r2->age = 21; > damon_add_region(r2, t); Let's allocate and setup 'ctx' and 'p' here. That will reduce alloc failure handling code. Also add 't' to 'ctx'. That will let us to remove damon_free_target() call from the final cleanup. > > - 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 +235,7 @@ 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 Thanks, SJ