Currently, when setting a cpuset's cpuset.cpus to a value that conflicts with its sibling partition, the sibling's partition state becomes invalid. However, this invalidation is often unnecessary.
For example: On a machine with 128 CPUs, there are m (m < 128) cpusets under the root cgroup. Each cpuset is used by a single user(user-1 use A1, ... , user-m use Am), and the partition states of these cpusets are configured as follows:
root cgroup / / \ \ A1 A2 ... An Am (root) (root) ... (root) (root/root invalid/member)
Assume that A1 through Am have not set cpuset.cpus.exclusive. When user-m modifies Am's cpuset.cpus to "0-127", it will cause all partition states from A1 to An to change from root to root invalid, as shown below.
root cgroup / / \ \ A1 A2 ... An Am (root invalid) (root invalid) ... (root invalid) (root invalid/member)
This outcome is entirely undeserved for all users from A1 to An.
This patch prevents such outcomes by ensuring that modifications to cpuset.cpus do not affect the partition state of other sibling cpusets. Therefore, with this patch applied, when user-m configures Am's cpuset.cpus to "0-127", the result will be as follows.
root cgroup / / \ \ A1 A2 ... An Am (root) (root) ... (root) (root invalid/member)
It is worth noting that, since this patch enforces the exclusivity of sibling cpusets, setting exclusivity now follows a "first-come, first-served" principle.
For example, consider the following four steps: before applying this patch, regardless of the order in which they are executed, the final partition state of both A1 and B1 would always be "root invalid."
Step | A1's prstate | B1's prstate | #1> echo "0-1" > A1/cpuset.cpus | member | member | #2> echo "root" > A1/cpuset.cpus.partition | root | member | #3> echo "1-2" > B1/cpuset.cpus | root invalid | member | #4> echo "root" > B1/cpuset.cpus.partition | root invalid | root invalid |
After applying this patch, the first party to set "root" will maintain its exclusive validity. As follows:
Step | A1's prstate | B1's prstate | #1> echo "0-1" > A1/cpuset.cpus | member | member | #2> echo "root" > A1/cpuset.cpus.partition | root | member | #3> echo "1-2" > B1/cpuset.cpus | root | member | #4> echo "root" > B1/cpuset.cpus.partition | root | root invalid |
Step | A1's prstate | B1's prstate | #1> echo "0-1" > B1/cpuset.cpus | member | member | #2> echo "root" > B1/cpuset.cpus.partition | member | root | #3> echo "1-2" > A1/cpuset.cpus | member | root | #4> echo "root" > A1/cpuset.cpus.partition | root invalid | root |
In summary, if the current cpuset conflicts with its sibling cpusets on exclusive CPUs (If a cpuset is exclusive and its exclusive CPUs are empty, its allowed CPUs will be treated as exclusive CPUs), only the current cpuset should bear the consequences.
Signed-off-by: Sun Shaojie sunshaojie@kylinos.cn --- kernel/cgroup/cpuset-internal.h | 3 + kernel/cgroup/cpuset-v1.c | 19 ++++++ kernel/cgroup/cpuset.c | 60 ++++++++++++------- .../selftests/cgroup/test_cpuset_prs.sh | 12 ++-- 4 files changed, 65 insertions(+), 29 deletions(-)
diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h index 337608f408ce..c53111998432 100644 --- a/kernel/cgroup/cpuset-internal.h +++ b/kernel/cgroup/cpuset-internal.h @@ -292,6 +292,7 @@ void cpuset1_hotplug_update_tasks(struct cpuset *cs, struct cpumask *new_cpus, nodemask_t *new_mems, bool cpus_updated, bool mems_updated); int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial); +bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2); #else static inline void fmeter_init(struct fmeter *fmp) {} static inline void cpuset1_update_task_spread_flags(struct cpuset *cs, @@ -302,6 +303,8 @@ static inline void cpuset1_hotplug_update_tasks(struct cpuset *cs, bool cpus_updated, bool mems_updated) {} static inline int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial) { return 0; } +static inline bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, + struct cpuset *cs2) {return false; } #endif /* CONFIG_CPUSETS_V1 */
#endif /* __CPUSET_INTERNAL_H */ diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c index 12e76774c75b..5aa0ac092ef6 100644 --- a/kernel/cgroup/cpuset-v1.c +++ b/kernel/cgroup/cpuset-v1.c @@ -373,6 +373,25 @@ int cpuset1_validate_change(struct cpuset *cur, struct cpuset *trial) return ret; }
+/* + * cpuset1_cpus_excl_conflict() - Check if two cpusets have exclusive CPU conflicts + * to legacy (v1) + * @cs1: first cpuset to check + * @cs2: second cpuset to check + * + * Returns: true if CPU exclusivity conflict exists, false otherwise + * + * If either cpuset is CPU exclusive, their allowed CPUs cannot intersect. + */ +bool cpuset1_cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) +{ + if (is_cpu_exclusive(cs1) || is_cpu_exclusive(cs2)) + return cpumask_intersects(cs1->cpus_allowed, + cs2->cpus_allowed); + + return false; +} + #ifdef CONFIG_PROC_PID_CPUSET /* * proc_cpuset_show() diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 52468d2c178a..e58dd26e074a 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -586,14 +586,24 @@ 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 + * For cgroup-v1: + * see cpuset1_cpus_excl_conflict() + * For cgroup-v2: + * 1. If both cs1 and cs2 are exclusive, cs1 and cs2 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 + * 4. If a cpuset is exclusive and its exclusive CPUs are empty, its allowed CPUs + * will be treated as exclusive CPUs; therefore, its allowed CPUs must not + * intersect with 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)) + /* For cgroup-v1 */ + if (!cpuset_v2()) + return cpuset1_cpus_excl_conflict(cs1, cs2); + + /* If 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 */ @@ -609,6 +619,20 @@ static inline bool cpus_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) cpumask_subset(cs2->cpus_allowed, cs1->exclusive_cpus)) return true;
+ /* + * When a cpuset is exclusive and its exclusive CPUs are empty, + * its cpus_allowed cannot intersect with another cpuset's exclusive_cpus. + */ + if (is_cpu_exclusive(cs1) && + cpumask_empty(cs1->exclusive_cpus) && + cpumask_intersects(cs1->cpus_allowed, cs2->exclusive_cpus)) + return true; + + if (is_cpu_exclusive(cs2) && + cpumask_empty(cs2->exclusive_cpus) && + cpumask_intersects(cs2->cpus_allowed, cs1->exclusive_cpus)) + return true; + return false; }
@@ -2411,34 +2435,17 @@ static int cpus_allowed_validate_change(struct cpuset *cs, struct cpuset *trialc struct tmpmasks *tmp) { int retval; - struct cpuset *parent = parent_cs(cs);
retval = validate_change(cs, trialcs);
if ((retval == -EINVAL) && cpuset_v2()) { - struct cgroup_subsys_state *css; - struct cpuset *cp; - /* * The -EINVAL error code indicates that partition sibling * CPU exclusivity rule has been violated. We still allow * the cpumask change to proceed while invalidating the - * partition. However, any conflicting sibling partitions - * have to be marked as invalid too. + * partition. */ trialcs->prs_err = PERR_NOTEXCL; - rcu_read_lock(); - cpuset_for_each_child(cp, css, parent) { - struct cpumask *xcpus = user_xcpus(trialcs); - - if (is_partition_valid(cp) && - cpumask_intersects(xcpus, cp->effective_xcpus)) { - rcu_read_unlock(); - update_parent_effective_cpumask(cp, partcmd_invalidate, NULL, tmp); - rcu_read_lock(); - } - } - rcu_read_unlock(); retval = 0; } return retval; @@ -2506,8 +2513,15 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, if (alloc_tmpmasks(&tmp)) return -ENOMEM;
- compute_trialcs_excpus(trialcs, cs); - trialcs->prs_err = PERR_NONE; + /* + * if there is exclusive CPUs conflict with the siblings, + * we still allow the cpumask change to proceed while + * invalidating the partition. + */ + if (compute_trialcs_excpus(trialcs, cs)) + trialcs->prs_err = PERR_NOTEXCL; + else + trialcs->prs_err = PERR_NONE;
retval = cpus_allowed_validate_change(cs, trialcs, &tmp); if (retval < 0) diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index a17256d9f88a..75154e22c702 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" " 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" " 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" - " 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" + # A non-exclusive cpuset.cpus change will not invalidate its siblings partition. + " 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 A1:0-1|B1:2-3 A1:P-1|B1:P1" + " 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"