Currently, when setting a cpuset's cpuset.cpus to a value that conflicts with the cpuset.cpus/cpuset.cpus.exclusive of a sibling partition, the sibling's partition state becomes invalid. This is overly harsh and is probably not necessary.
The cpuset.cpus.exclusive control file, if set, will override the cpuset.cpus of the same cpuset when creating a cpuset partition. So cpuset.cpus has less priority than cpuset.cpus.exclusive in setting up a partition. However, it cannot override a conflicting cpuset.cpus file in a sibling cpuset and the partition creation process will fail. This is inconsistent. That will also make using cpuset.cpus.exclusive less valuable as a tool to set up cpuset partitions as the users have to check if such a cpuset.cpus conflict exists or not.
Fix these problems by strictly adhering to the setting of the following control files in descending order of priority when setting up a partition.
1. cpuset.cpus.exclusive.effective of a valid partition 2. cpuset.cpus.exclusive 3. cpuset.cpus
So once a cpuset.cpus.exclusive is set without failure, it will always be allowed to form a valid partition as long as at least one CPU can be granted from its parent irrespective of the state of the siblings' cpuset.cpus values. Of course, setting cpuset.cpus.exclusive will fail if it conflicts with the cpuset.cpus.exclusive or the cpuset.cpus.exclusive.effective value of a sibling.
Partition can still be created by setting only cpuset.cpus without setting cpuset.cpus.exclusive. However, any conflicting CPUs in sibling's cpuset.cpus.exclusive.effective and cpuset.cpus.exclusive values will be removed from its cpuset.cpus.exclusive.effective as long as there is still one or more CPUs left and can be granted from its parent. This CPU stripping is currently done in rm_siblings_excl_cpus().
The new code will now try its best to enable the creation of new partitions with only cpuset.cpus set without invalidating existing ones. However it is not guaranteed that all the CPUs requested in cpuset.cpus will be used in the new partition even when all these CPUs can be granted from the parent.
This is similar to the fact that cpuset.cpus.effective may not be able to include all the CPUs requested in cpuset.cpus. In this case, the parent may not able to grant all the exclusive CPUs requested in cpuset.cpus to cpuset.cpus.exclusive.effective if some of them have already been granted to other partitions earlier.
With the creation of multiple sibling partitions by setting only cpuset.cpus, this does have the side effect that their exact cpuset.cpus.exclusive.effective settings will depend on the order of partition creation if there are conflicts.
For example, # echo "0-2" > A1/cpuset.cpus # echo "root" > A1/cpuset.cpus.partition # echo A1/cpuset.cpus.partition root # echo A1/cpuset.cpus.exclusive.effective 0-2 # echo "2-4" > B1/cpuset.cpus # echo "root" > B1/cpuset.cpus.partition # echo B1/cpuset.cpus.partition root # echo B1/cpuset.cpus.exclusive.effective 3-4 # echo B1/cpuset.cpus.effective 3-4
For users who want to be sure that they can get all the CPUs they want, cpuset.cpus.exclusive should be used instead if they can set cpuset.cpus.exclusive without failure.
To make this change, we have to separate out the is_cpu_exclusive() check in cpus_excl_conflict() into a cgroup v1 only cpuset1_cpus_excl_conflict() helper. The cpus_allowed_validate_change() helper is also no longer need and can now be removed.
Some existing tests in test_cpuset_prs.sh are updated and new ones are added to reflect the new behavior.
Reported-by: Sun Shaojie sunshaojie@kylinos.cn Closes: https://lore.kernel.org/lkml/20251117015708.977585-1-sunshaojie@kylinos.cn/ Signed-off-by: Waiman Long longman@redhat.com --- kernel/cgroup/cpuset-internal.h | 3 + kernel/cgroup/cpuset-v1.c | 19 +++++ kernel/cgroup/cpuset.c | 81 +++++++------------ .../selftests/cgroup/test_cpuset_prs.sh | 26 ++++-- 4 files changed, 68 insertions(+), 61 deletions(-)
diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h index e718a4f54360..e8e2683cb067 100644 --- a/kernel/cgroup/cpuset-internal.h +++ b/kernel/cgroup/cpuset-internal.h @@ -312,6 +312,7 @@ 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); void cpuset1_init(struct cpuset *cs); void cpuset1_online_css(struct cgroup_subsys_state *css); int cpuset1_generate_sched_domains(cpumask_var_t **domains, @@ -326,6 +327,8 @@ 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; } static inline void cpuset1_init(struct cpuset *cs) {} static inline void cpuset1_online_css(struct cgroup_subsys_state *css) {} static inline int cpuset1_generate_sched_domains(cpumask_var_t **domains, diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c index ecfea7800f0d..04124c38a774 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 83bf6b588e5f..c7e54d090c7b 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -129,6 +129,18 @@ static bool force_sd_rebuild; * For simplicity, a local partition can be created under a local or remote * partition but a remote partition cannot have any partition root in its * ancestor chain except the cgroup root. + * + * A valid partition can be formed by setting either cpus_allowed or + * exclusive_cpus. If there are exclusive CPU conflicts, the conflicting + * CPUs will be assigned to the effective_xcpus of the partition according + * to the appearance of those CPUs in cpumasks (in descending order of + * priority). + * 1. effective_xcpus of a valid partition + * 2. exclusive_cpus + * 3. cpus_allowed + * + * exclusive_cpus should be used for setting up partition if the users want + * to get as many CPUs as possible. */ #define PRS_MEMBER 0 #define PRS_ROOT 1 @@ -616,27 +628,25 @@ 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 - * 2. exclusive_cpus masks cannot intersect between cpusets - * 3. The allowed CPUs of a sibling cpuset cannot be a subset of the new exclusive CPUs + * o cgroup v1 + * See cpuset1_cpus_excl_conflict() + * o cgroup v2 + * - The exclusive_cpus values cannot overlap. + * - New exclusive_cpus cannot be a superset of a sibling's cpus_allowed. */ static inline bool cpus_excl_conflict(struct cpuset *trial, struct cpuset *sibling, bool new_xcpus) { - /* If either cpuset is exclusive, check if they are mutually exclusive */ - if (is_cpu_exclusive(trial) || is_cpu_exclusive(sibling)) - return !cpusets_are_exclusive(trial, sibling); - - /* Exclusive_cpus cannot intersect */ - if (cpumask_intersects(trial->exclusive_cpus, sibling->exclusive_cpus)) - return true; + if (!cpuset_v2()) + return cpuset1_cpus_excl_conflict(trial, sibling);
/* The cpus_allowed of a sibling cpuset cannot be a subset of the new exclusive_cpus */ if (new_xcpus && !cpumask_empty(sibling->cpus_allowed) && cpumask_subset(sibling->cpus_allowed, trial->exclusive_cpus)) return true;
- return false; + /* Exclusive_cpus cannot intersect */ + return cpumask_intersects(trial->exclusive_cpus, sibling->exclusive_cpus); }
static inline bool mems_excl_conflict(struct cpuset *cs1, struct cpuset *cs2) @@ -2306,43 +2316,6 @@ static enum prs_errcode validate_partition(struct cpuset *cs, struct cpuset *tri return PERR_NONE; }
-static int cpus_allowed_validate_change(struct cpuset *cs, struct cpuset *trialcs, - 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. - */ - 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; -} - /** * partition_cpus_change - Handle partition state changes due to CPU mask updates * @cs: The target cpuset being modified @@ -2402,15 +2375,15 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, if (cpumask_equal(cs->cpus_allowed, trialcs->cpus_allowed)) return 0;
- if (alloc_tmpmasks(&tmp)) - return -ENOMEM; - compute_trialcs_excpus(trialcs, cs); trialcs->prs_err = PERR_NONE;
- retval = cpus_allowed_validate_change(cs, trialcs, &tmp); + retval = validate_change(cs, trialcs); if (retval < 0) - goto out_free; + return retval; + + if (alloc_tmpmasks(&tmp)) + return -ENOMEM;
/* * Check all the descendants in update_cpumasks_hier() if @@ -2433,7 +2406,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, /* Update CS_SCHED_LOAD_BALANCE and/or sched_domains, if necessary */ if (cs->partition_root_state) update_partition_sd_lb(cs, old_prs); -out_free: + free_tmpmasks(&tmp); return retval; } diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh index a17256d9f88a..ff4540b0490e 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|XA1:0-1|B1:2-3 A1:P1|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" @@ -417,6 +417,14 @@ TEST_MATRIX=( " CX1-4:S+ CX2-4:P2 . C5-6 . . . P1:C3-6 0 A1:1|A2:2-4|B1:5-6 \ A1:P0|A2:P2:B1:P-1 2-4"
+ # When multiple partitions with conflicting cpuset.cpus are created, the + # latter created ones will only get what are left of the available exclusive + # CPUs. + " C1-3:P1 . . . . . . C3-5:P1 0 A1:1-3|B1:4-5:XB1:4-5 A1:P1|B1:P1" + + # cpuset.cpus can be set to a subset of sibling's cpuset.cpus.exclusive + " C1-3:X1-3 . . C4-5 . . . C1-2 0 A1:1-3|B1:1-2" + # old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS # ------ ------ ------ ------ ------ ------ ------ ------ ---- ----- ------ -------- # Failure cases: @@ -427,7 +435,7 @@ TEST_MATRIX=( # Changes to cpuset.cpus.exclusive that violate exclusivity rule is rejected " C0-3 . . C4-5 X0-3 . . X3-5 1 A1:0-3|B1:4-5"
- # cpuset.cpus cannot be a subset of sibling cpuset.cpus.exclusive + # cpuset.cpus.exclusive cannot be set to a superset of sibling's cpuset.cpus " C0-3 . . C4-5 X3-5 . . . 1 A1:0-3|B1:4-5" )
@@ -477,6 +485,10 @@ REMOTE_TEST_MATRIX=( . . X1-2:P2 X4-5:P1 . X1-7:P2 p1:3|c11:1-2|c12:4:c22:5-6 \ p1:P0|p2:P1|c11:P2|c12:P1|c22:P2 \ 1-2,4-6|1-2,5-6" + # c12 whose cpuset.cpus CPUs are all granted to c11 will become invalid partition + " C1-5:P1:S+ . C1-4:P1 C2-3 . . \ + . . . P1 . . p1:5|c11:1-4|c12:5 \ + p1:P1|c11:P1|c12:P-1" )
#