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Message-Id: <20251112021120.248778-1-sunshaojie@kylinos.cn>
Date: Wed, 12 Nov 2025 10:11:20 +0800
From: Sun Shaojie <sunshaojie@...inos.cn>
To: longman@...hat.com
Cc: tj@...nel.org,
hannes@...xchg.org,
mkoutny@...e.com,
shuah@...nel.org,
cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org,
Sun Shaojie <sunshaojie@...inos.cn>
Subject: [PATCH v1] cpuset: Avoid unnecessary partition invalidation
Currently, when a non-exclusive cpuset's "cpuset.cpus" overlaps with a
partitioned sibling, the sibling's partition state becomes invalid.
However, this invalidation is often unnecessary.
This can be observed in specific configuration sequences:
Case 1: Partition created first, then non-exclusive cpuset overlaps
#1> mkdir -p /sys/fs/cgroup/A1
#2> echo "0-1" > /sys/fs/cgroup/A1/cpuset.cpus
#3> echo "root" > /sys/fs/cgroup/A1/cpuset.cpus.partition
#4> mkdir -p /sys/fs/cgroup/B1
#5> echo "0-3" > /sys/fs/cgroup/B1/cpuset.cpus
// A1's partition becomes "root invalid" - this is unnecessary
Case 2: Non-exclusive cpuset exists first, then partition created
#1> mkdir -p /sys/fs/cgroup/B1
#2> echo "0-1" > /sys/fs/cgroup/B1/cpuset.cpus
#3> mkdir -p /sys/fs/cgroup/A1
#4> echo "0-1" > /sys/fs/cgroup/A1/cpuset.cpus
#5> echo "root" > /sys/fs/cgroup/A1/cpuset.cpus.partition
// A1's partition becomes "root invalid" - this is unnecessary
In Case 1, the effective CPU mask of B1 can differ from its requested
mask. B1 can use CPUs 2-3 which don't overlap with A1's exclusive
CPUs (0-1), thus not violating A1's exclusivity requirement.
In Case 2, B1 can inherit the effective CPUs from its parent, so there
is no need to invalidate A1's partition state.
This patch relaxes the overlap check to only consider conflicts between
partitioned siblings, not between a partitioned cpuset and a regular
non-exclusive one.
Signed-off-by: Sun Shaojie <sunshaojie@...inos.cn>
---
kernel/cgroup/cpuset.c | 8 ++++----
tools/testing/selftests/cgroup/test_cpuset_prs.sh | 10 +++++-----
2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 52468d2c178a..e0d27c9a101a 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -586,14 +586,14 @@ static inline bool cpusets_are_exclusive(struct cpuset *cs1, struct cpuset *cs2)
* Returns: true if CPU exclusivity conflict exists, false otherwise
*
* Conflict detection rules:
- * 1. If either cpuset is CPU exclusive, they must be mutually exclusive
+ * 1. If both cpusets are exclusive, they must be mutually exclusive
* 2. exclusive_cpus masks cannot intersect between cpusets
* 3. The allowed CPUs of one cpuset cannot be a subset of another's exclusive CPUs
*/
static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2)
{
- /* If either cpuset is exclusive, check if they are mutually exclusive */
- if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2))
+ /* If both cpusets are exclusive, check if they are mutually exclusive */
+ if (is_cpu_exclusive(cs1) && is_cpu_exclusive(cs2))
return !cpusets_are_exclusive(cs1, cs2);
/* Exclusive_cpus cannot intersect */
@@ -695,7 +695,7 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
goto out;
/*
- * If either I or some sibling (!= me) is exclusive, we can't
+ * If both I and some sibling (!= me) are exclusive, we can't
* overlap. exclusive_cpus cannot overlap with each other if set.
*/
ret = -EINVAL;
diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
index a17256d9f88a..903dddfe88d7 100755
--- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
+++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
@@ -269,7 +269,7 @@ TEST_MATRIX=(
" C0-3:S+ C1-3:S+ C2-3 . X2-3 X3:P2 . . 0 A1:0-2|A2:3|A3:3 A1:P0|A2:P2 3"
" C0-3:S+ C1-3:S+ C2-3 . X2-3 X2-3 X2-3:P2 . 0 A1:0-1|A2:1|A3:2-3 A1:P0|A3:P2 2-3"
" C0-3:S+ C1-3:S+ C2-3 . X2-3 X2-3 X2-3:P2:C3 . 0 A1:0-1|A2:1|A3:2-3 A1:P0|A3:P2 2-3"
- " C0-3:S+ C1-3:S+ C2-3 C2-3 . . . P2 0 A1:0-3|A2:1-3|A3:2-3|B1:2-3 A1:P0|A3:P0|B1:P-2"
+ " C0-3:S+ C1-3:S+ C2-3 C2-3 . . . P2 0 A1:0-1|A2:1|A3:1|B1:2-3 A1:P0|A3:P0|B1:P2 2-3"
" C0-3:S+ C1-3:S+ C2-3 C4-5 . . . P2 0 B1:4-5 B1:P2 4-5"
" C0-3:S+ C1-3:S+ C2-3 C4 X2-3 X2-3 X2-3:P2 P2 0 A3:2-3|B1:4 A3:P2|B1:P2 2-4"
" C0-3:S+ C1-3:S+ C2-3 C4 X2-3 X2-3 X2-3:P2:C1-3 P2 0 A3:2-3|B1:4 A3:P2|B1:P2 2-4"
@@ -318,7 +318,7 @@ TEST_MATRIX=(
# Invalid to valid local partition direct transition tests
" C1-3:S+:P2 X4:P2 . . . . . . 0 A1:1-3|XA1:1-3|A2:1-3:XA2: A1:P2|A2:P-2 1-3"
" C1-3:S+:P2 X4:P2 . . . X3:P2 . . 0 A1:1-2|XA1:1-3|A2:3:XA2:3 A1:P2|A2:P2 1-3"
- " C0-3:P2 . . C4-6 C0-4 . . . 0 A1:0-4|B1:4-6 A1:P-2|B1:P0"
+ " C0-3:P2 . . C4-6 C0-4 . . . 0 A1:0-4|B1:5-6 A1:P2|B1:P0 0-4"
" C0-3:P2 . . C4-6 C0-4:C0-3 . . . 0 A1:0-3|B1:4-6 A1:P2|B1:P0 0-3"
# Local partition invalidation tests
@@ -388,10 +388,10 @@ TEST_MATRIX=(
" C0-1:S+ C1 . C2-3 . P2 . . 0 A1:0-1|A2:1 A1:P0|A2:P-2"
" C0-1:S+ C1:P2 . C2-3 P1 . . . 0 A1:0|A2:1 A1:P1|A2:P2 0-1|1"
- # A non-exclusive cpuset.cpus change will invalidate partition and its siblings
- " C0-1:P1 . . C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P0"
+ # A non-exclusive cpuset.cpus change will not invalidate partition and its siblings
+ " C0-1:P1 . . C2-3 C0-2 . . . 0 A1:0-2|B1:3 A1:P1|B1:P0"
" C0-1:P1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P-1|B1:P-1"
- " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-2|B1:2-3 A1:P0|B1:P-1"
+ " C0-1 . . P1:C2-3 C0-2 . . . 0 A1:0-1|B1:2-3 A1:P0|B1:P1"
# cpuset.cpus can overlap with sibling cpuset.cpus.exclusive but not subsumed by it
" C0-3 . . C4-5 X5 . . . 0 A1:0-3|B1:4-5"
--
2.25.1
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