From: Andrew Morton <akpm@linux-foundation.org>
To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,akpm@linux-foundation.org
Subject: + mm-damon-vaddr-drop-last-same-folio-access-check-optimization.patch added to mm-new branch
Date: Tue, 14 Jul 2026 21:45:24 -0700 [thread overview]
Message-ID: <20260715044525.2ED2F1F00A3A@smtp.kernel.org> (raw)
The patch titled
Subject: mm/damon/vaddr: drop last same folio access check optimization
has been added to the -mm mm-new branch. Its filename is
mm-damon-vaddr-drop-last-same-folio-access-check-optimization.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-vaddr-drop-last-same-folio-access-check-optimization.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
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------------------------------------------------------
From: SJ Park <sj@kernel.org>
Subject: mm/damon/vaddr: drop last same folio access check optimization
Date: Tue, 14 Jul 2026 20:09:58 -0700
The optimization can race when multiple kdamonds are running. Meanwhile,
the impact of the optimization is quite doubtful. Just remove it.
The user impact of the issue should be quite trivial. After all, the race
can happen only when the user intentionally setup DAMON in the way. Even
if it happens, it would be rare and only degrade the best-effort
monitoring results. No critical consequences like kernel panic or memory
corruption happen.
The race possibility was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260715031002.108504-4-sj@kernel.org
Link: https://lore.kernel.org/20260621204050.10993-1-sj@kernel.org [1]
Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 5.15.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/damon/vaddr.c | 33 ++++++---------------------------
1 file changed, 6 insertions(+), 27 deletions(-)
--- a/mm/damon/vaddr.c~mm-damon-vaddr-drop-last-same-folio-access-check-optimization
+++ a/mm/damon/vaddr.c
@@ -383,8 +383,6 @@ static void damon_va_prepare_access_chec
}
struct damon_young_walk_private {
- /* size of the folio for the access checked virtual memory address */
- unsigned long *folio_sz;
bool young;
};
@@ -411,7 +409,6 @@ static int damon_young_pmd_entry(pmd_t *
mmu_notifier_test_young(walk->mm,
addr))
priv->young = true;
- *priv->folio_sz = HPAGE_PMD_SIZE;
huge_out:
spin_unlock(ptl);
return 0;
@@ -430,7 +427,6 @@ huge_out:
if (pte_young(ptent) || !folio_test_idle(folio) ||
mmu_notifier_test_young(walk->mm, addr))
priv->young = true;
- *priv->folio_sz = folio_size(folio);
out:
pte_unmap_unlock(pte, ptl);
return 0;
@@ -458,7 +454,6 @@ static int damon_young_hugetlb_entry(pte
if (pte_young(entry) || !folio_test_idle(folio) ||
mmu_notifier_test_young(walk->mm, addr))
priv->young = true;
- *priv->folio_sz = huge_page_size(h);
folio_put(folio);
@@ -470,11 +465,9 @@ out:
#define damon_young_hugetlb_entry NULL
#endif /* CONFIG_HUGETLB_PAGE */
-static bool damon_va_young(struct mm_struct *mm, unsigned long addr,
- unsigned long *folio_sz)
+static bool damon_va_young(struct mm_struct *mm, unsigned long addr)
{
struct damon_young_walk_private arg = {
- .folio_sz = folio_sz,
.young = false,
};
@@ -494,28 +487,17 @@ static bool damon_va_young(struct mm_str
* r the region to be checked
*/
static void __damon_va_check_access(struct mm_struct *mm,
- struct damon_region *r, bool same_target)
+ struct damon_region *r)
{
- static unsigned long last_addr;
- static unsigned long last_folio_sz = PAGE_SIZE;
- static bool last_accessed;
+ bool accessed;
if (!mm) {
damon_update_region_access_rate(r, false);
return;
}
- /* If the region is in the last checked page, reuse the result */
- if (same_target && (ALIGN_DOWN(last_addr, last_folio_sz) ==
- ALIGN_DOWN(r->sampling_addr, last_folio_sz))) {
- damon_update_region_access_rate(r, last_accessed);
- return;
- }
-
- last_accessed = damon_va_young(mm, r->sampling_addr, &last_folio_sz);
- damon_update_region_access_rate(r, last_accessed);
-
- last_addr = r->sampling_addr;
+ accessed = damon_va_young(mm, r->sampling_addr);
+ damon_update_region_access_rate(r, accessed);
}
static unsigned int damon_va_check_accesses(struct damon_ctx *ctx)
@@ -524,15 +506,12 @@ static unsigned int damon_va_check_acces
struct mm_struct *mm;
struct damon_region *r;
unsigned int max_nr_accesses = 0;
- bool same_target;
damon_for_each_target(t, ctx) {
mm = damon_get_mm(t);
- same_target = false;
damon_for_each_region(r, t) {
- __damon_va_check_access(mm, r, same_target);
+ __damon_va_check_access(mm, r);
max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
- same_target = true;
}
if (mm)
mmput(mm);
_
Patches currently in -mm which might be from sj@kernel.org are
samples-damon-wsse-handle-damon_start-failure.patch
samples-damon-prcl-handle-damon_start-failure.patch
samples-damon-mtier-handle-damon_start-failure.patch
samples-damon-mtier-handle-damon_stop-failure.patch
samples-damon-wsse-stop-and-free-damon-ctx-when-damon_call-fails.patch
samples-damon-prcl-stop-and-free-damon-ctx-when-damon_call-fails.patch
mm-damon-sysfs-kobject_del-target-normal-context-and-kdamond-dirs.patch
mm-damon-sysfs-kobject_del-region-and-target-error-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-region-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-filter-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-quota-goal-dirs.patch
mm-damon-sysfs-schemes-kobject_del-scheme-action-destination-dirs.patch
mm-damon-sysfs-kobject_del-probe-dirs.patch
mm-damon-sysfs-kobject_del-probe-filter-dirs.patch
mm-damon-sysfs-kobject_del-probe-dirs-in-probes_addd_dir-error-path.patch
mm-damon-sysfs-schemes-kobject_del-region-for-populate_region-error.patch
docs-mm-damon-design-update-for-damos_quota_node_eligible_mem_bp.patch
docs-abi-damon-document-probe-files.patch
mm-damon-tests-core-kunit-test-damon_rand.patch
selftests-damon-sysfssh-test-multiple-probe-dirs-creation.patch
selftests-damon-sysfssh-test-coreops_filters-directories.patch
selftests-damon-sysfssh-test-dests-dir.patch
selftests-damon-sysfssh-test-all-files-in-quota-goal-dir.patch
mm-damon-core-reduce-range-setup-in-damon_commit_target_regions.patch
mm-damon-sysfs-split-probe-setup-function-out.patch
mm-damon-sysfs-split-out-filters-setup-function.patch
mm-damon-sysfs-fix-typos-in-probe_addrm_dirs-s-attr-probe.patch
mm-damon-core-introduce-damon_nr_accesses_mvsum.patch
mm-damon-tests-core-kunit-test-damon_mvsum.patch
mm-damon-core-always-update-last_nr_accesses-for-intervals-change.patch
mm-damon-core-handle-unreset-nr_accesses-in-damon_nr_accesses_mvsum.patch
mm-damon-core-use-damon_nr_accesses_mvsum-in-__damos_valid_target.patch
mm-damon-core-use-damon_nr_accesses_mvsum-for-damos-region-tracing.patch
mm-damon-sysfs-schemes-use-damon_nr_accesses_mvsum-for-damo-regions.patch
mm-damon-core-remove-damon_warn_fix_nr_accesses_corruption.patch
mm-damon-core-remove-damon_verify_reset_aggregated.patch
mm-damon-core-remove-damon_verify_merge_regions_of.patch
mm-damon-tests-core-kunit-remove-nr_accesses_bp-setup-and-tests.patch
selftests-damon-drgn_dump_damon_status-do-not-dump-nr_accesses_bp.patch
mm-damon-core-remove-nr_accesses_bp-setups-and-updates.patch
mm-damon-core-remove-attrs-param-from-damon_update_region_access_rate.patch
mm-damon-paddr-remove-attrs-param-from-__damon_pa_check_access.patch
mm-damon-vaddr-remove-attrs-param-from-__damon_va_check_access.patch
mm-damon-core-remove-damon_moving_sum-and-its-unit-test.patch
mm-damon-core-remove-damon_region-nr_accesses_bp.patch
mm-damon-add-damon_region-last_probe_hits.patch
mm-damon-core-introduce-damon_probe_hits_mvsum.patch
mm-damon-sysfs-schemes-set-probe-hits-as-pseudo-moving-sums.patch
mm-damon-core-safely-validate-src-on-damon_commit_ctx.patch
mm-damon-core-do-parameter-testing-commit-on-damon_start.patch
mm-damon-sysfs-remove-duplicated-commit-input-validity-check.patch
mm-damon-reclaim-remove-duplicated-min_region_sz-power-of-2-check.patch
mm-damon-lru_sort-remove-duplicated-min_region_sz-power_of_2-check.patch
mm-damon-document-region-size-validation-in-damon_set_regions.patch
mm-damon-core-remove-start-end-check-in-damon_set_region_system_rams.patch
mm-damon-sysfs-remove-region-size-validation.patch
mm-damon-core-stop-ctxs-in-damon_start-before-returning-an-error.patch
samples-damon-mtier-do-not-stop-first-context-for-damon_start-failure.patch
mm-damon-core-make-damon_stop-never-fails.patch
mm-damon-sysfs-ignore-damon_stop-return-value.patch
mm-damon-reclaaim-ignore-damon_stop-return-value.patch
mm-damon-lru_sort-ignore-damon_stop-return-value.patch
mm-damon-core-change-damon_stop-return-type-to-void.patch
samples-damon-mtier-stop-all-contexts-with-single-damon_stop-call.patch
mm-damon-core-wait-ctx-stop-in-damon_call-before-reruning-an-error.patch
samples-damon-wsse-do-not-stop-ctx-for-damon_call-failure.patch
samples-damon-prcl-do-not-stop-damon-for-damon_call-failure.patch
mm-damon-core-remove-comment-and-test-for-nr_to_bp-divide-by-zero.patch
mm-damon-core-s-damon_max_nr_accesses-damon_nr_samples_per_aggr.patch
mm-damon-core-s-accesses_bp_to_nr_accesses-sample_bp_to_count.patch
mm-damon-core-s-nr_accesses_to_accesses_bp-sample_count_to_bp.patch
mm-damon-core-s-nr_accesses_for_new_attrs-nr_samples_for_new_attrs.patch
mm-damon-core-update-probe-hits-for-new-parameter-commit.patch
mm-damon-core-handle-unreset-probe_hits-in-probe_hits_mvsum.patch
mm-damon-core-introduce-damon_probe-weight.patch
mm-damon-core-ask-apply_probes-ops-callback-to-set-sampling-address.patch
mm-damon-paddr-set-samples-in-apply_probes-if-requested.patch
mm-damon-core-ask-apply_probe-to-return-max-probe-hits-weighted-sum.patch
mm-damon-core-implement-damon_probe_hits_wsum.patch
mm-damon-paddr-respect-return_max_wsum.patch
mm-damon-core-use-abs_diff-instead-of-abs.patch
mm-damon-core-extend-merge-function-to-work-with-probe-hits.patch
mm-damon-core-disallow-probe_hits-overflow-on-attrs-only-monitoring.patch
mm-damon-core-validate-params-for-probe-hits-weighted-sum-overflow.patch
mm-damon-core-disable-access-monitoring-when-probe-weights-are-set.patch
mm-damon-core-set-samples-in-apply_probes-if-probe-weights-are-set.patch
mm-damon-core-s-max_nr_accesses-max_merge_score-in-kdamond_fn.patch
mm-damon-core-get-merge-threshold-from-probe-hits-when-weights-are-set.patch
mm-damon-core-implement-damon_has_probe_weight.patch
mm-damon-sysfs-implement-probe-weight-file.patch
docs-mm-damon-design-document-attrs-only-monitoring.patch
docs-admin-guide-mm-damon-usage-document-weight-sysfs-file.patch
docs-abi-damon-document-probe-weight-file.patch
mm-damon-core-skip-aging-from-repeated-aggressive-merging.patch
mm-damon-core-hide-private-damon_region-fields.patch
mm-damon-core-hide-private-damon_target-fields.patch
mm-damon-core-hide-private-damos_quota_goal-fields.patch
mm-damon-core-hide-private-damos_quota-fields.patch
mm-damon-core-hide-private-damos_filter-fields.patch
mm-damon-core-hide-private-damos-fields.patch
mm-damon-core-hide-private-damon_filter-fields.patch
mm-damon-core-hide-private-damon_probe-fields.patch
mm-damon-sysfs-do-not-directly-access-damon_ctx-ops.patch
mm-damon-core-hide-core-private-damon_ctx-fields.patch
mm-damon-core-avoid-infinite-kdamond_merge_regions-internal-loop.patch
mm-damon-tests-core-kunit-catch-test-failure-in-test_merge_regions_of.patch
mm-damon-vaddr-drop-last-same-folio-access-check-optimization.patch
mm-damon-paddr-drop-last-same-folio-access-check-reuse-optimization.patch
mm-damon-sysfs-read-addr_unit-only-once-in-damon_sysfs_apply_inputs.patch
mm-damon-sysfs-read-ops_id-only-once-in-damon_sysfs_apply_inputs.patch
reply other threads:[~2026-07-15 4:45 UTC|newest]
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