A cpuset partition is a collection of cpusets with a partition root
and its descendants from that root downward excluding any cpusets that
are part of other partitions. A partition has exclusive access to a set
of CPUs granted to it. Other cpusets outside of a partition cannot use
any CPUs in that set.
Currently, creation of partitions requires a hierarchical CPUs
distribution model where the parent of a partition root has to be
a partition root itself. Hence all the partition roots have to be
clustered around the cgroup root.
To enable the creation of a remote partition down in the hierarchy
without a parental partition root, we need a way to reserve the CPUs
that will be used in a remote partition. Introduce a new root-only
"cpuset.cpus.reserve" control file in the top cpuset for this particular
purpose.
By default, the new "cpuset.cpus.reserve" control file will track
the subparts_cpus cpumask in the top cpuset. By writing into this new
control file, however, we can reserve additional CPUs that can be used
in a remote partition. Any CPUs that are in "cpuset.cpus.reserve" will
have to be removed from the effective_cpus of all the cpusets that are
not part of that valid partitions.
The prefix "+" and "-" can be used to indicate the addition to or the
subtraction from the existing CPUs in "cpuset.cpus.reserve". A single
"-" character indicate the deletion of all the free reserve CPUs not
allocated to any existing partition.
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 253 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 239 insertions(+), 14 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 8604c919e1e4..69abe95a9969 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -208,7 +208,33 @@ struct cpuset {
struct cgroup_file partition_file;
};
-static cpumask_var_t cs_tmp_cpus; /* Temp cpumask for partition */
+/*
+ * Reserved CPUs for partitions.
+ *
+ * By default, CPUs used in partitions are tracked in the parent's
+ * subparts_cpus mask following a hierarchical CPUs distribution model.
+ * To enable the creation of a remote partition down in the hierarchy
+ * without a parental partition root, one can write directly to
+ * cpuset.cpus.reserve in the root cgroup to allocate more CPUs that can
+ * be used by remote partitions. Removal of existing reserved CPUs may
+ * also cause some existing partitions to become invalid.
+ *
+ * All the cpumasks below should only be used with cpuset_mutex held.
+ * Modification of cs_reserve_cpus & cs_free_reserve_cpus also requires
+ * holding the callback_lock.
+ *
+ * Relationship among cs_reserve_cpus, cs_free_reserve_cpus and
+ * top_cpuset.subparts_cpus are:
+ *
+ * top_cpuset.subparts_cpus ⊆ cs_reserve_cpus
+ * cs_free_reserve_cpus ⊆ cs_reserve_cpus
+ * top_cpuset.subparts_cpus ∩ cs_free_reserve_cpus = ∅
+ * cs_reserve_cpus - cs_free_reserve_cpus - top_cpuset.subparts_cpus
+ * = CPUs dedicated to remote partitions
+ */
+static cpumask_var_t cs_reserve_cpus; /* Reserved CPUs */
+static cpumask_var_t cs_free_reserve_cpus; /* Unallocated reserved CPUs */
+static cpumask_var_t cs_tmp_cpus; /* Temp cpumask for partition */
/*
* Partition root states:
@@ -1202,13 +1228,13 @@ static void rebuild_sched_domains_locked(void)
* should be the same as the active CPUs, so checking only top_cpuset
* is enough to detect racing CPU offlines.
*/
- if (!top_cpuset.nr_subparts_cpus &&
+ if (cpumask_empty(cs_reserve_cpus) &&
!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
return;
/*
* With subpartition CPUs, however, the effective CPUs of a partition
- * root should be only a subset of the active CPUs. Since a CPU in any
+ * root should only be a subset of the active CPUs. Since a CPU in any
* partition root could be offlined, all must be checked.
*/
if (top_cpuset.nr_subparts_cpus) {
@@ -1275,7 +1301,7 @@ static void update_tasks_cpumask(struct cpuset *cs, struct cpumask *new_cpus)
*/
if ((task->flags & PF_KTHREAD) && kthread_is_per_cpu(task))
continue;
- cpumask_andnot(new_cpus, possible_mask, cs->subparts_cpus);
+ cpumask_andnot(new_cpus, possible_mask, cs_reserve_cpus);
} else {
cpumask_and(new_cpus, possible_mask, cs->effective_cpus);
}
@@ -1406,6 +1432,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
int deleting; /* Moving cpus from subparts_cpus to effective_cpus */
int old_prs, new_prs;
int part_error = PERR_NONE; /* Partition error? */
+ bool update_reserve = (parent == &top_cpuset);
lockdep_assert_held(&cpuset_mutex);
@@ -1576,7 +1603,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
}
/*
- * Change the parent's subparts_cpus.
+ * Change the parent's subparts_cpus and maybe cs_reserve_cpus.
* Newly added CPUs will be removed from effective_cpus and
* newly deleted ones will be added back to effective_cpus.
*/
@@ -1586,10 +1613,25 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
parent->subparts_cpus, tmp->addmask);
cpumask_andnot(parent->effective_cpus,
parent->effective_cpus, tmp->addmask);
+ if (update_reserve) {
+ cpumask_or(cs_reserve_cpus,
+ cs_reserve_cpus, tmp->addmask);
+ cpumask_andnot(cs_free_reserve_cpus,
+ cs_free_reserve_cpus, tmp->addmask);
+ }
}
if (deleting) {
cpumask_andnot(parent->subparts_cpus,
parent->subparts_cpus, tmp->delmask);
+ /*
+ * The automatic cpu reservation of adjacent partition
+ * won't add back the deleted CPUs to cs_free_reserve_cpus.
+ * Instead, they are returned back to effective_cpus of top
+ * cpuset.
+ */
+ if (update_reserve)
+ cpumask_andnot(cs_reserve_cpus,
+ cs_reserve_cpus, tmp->delmask);
/*
* Some of the CPUs in subparts_cpus might have been offlined.
*/
@@ -1783,6 +1825,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
if (need_rebuild_sched_domains)
rebuild_sched_domains_locked();
+
+ return;
}
/**
@@ -1955,6 +1999,167 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
return 0;
}
+/**
+ * update_reserve_cpumask - update cs_reserve_cpus
+ * @trialcs: trial cpuset
+ * @buf: buffer of cpu numbers written to this cpuset
+ * Return: 0 if successful, < 0 if error
+ */
+static int update_reserve_cpumask(struct cpuset *trialcs, const char *buf)
+{
+ struct cgroup_subsys_state *css;
+ struct cpuset *cs;
+ bool adding, deleting;
+ struct tmpmasks tmp;
+
+ adding = deleting = false;
+ if (*buf == '+') {
+ adding = true;
+ buf++;
+ } else if (*buf == '-') {
+ deleting = true;
+ buf++;
+ }
+
+ if (!*buf) {
+ if (adding)
+ return -EINVAL;
+
+ if (deleting) {
+ if (cpumask_empty(cs_free_reserve_cpus))
+ return 0;
+ cpumask_copy(trialcs->cpus_allowed, cs_free_reserve_cpus);
+ } else {
+ cpumask_clear(trialcs->cpus_allowed);
+ }
+ } else {
+ int retval = cpulist_parse(buf, trialcs->cpus_allowed);
+
+ if (retval < 0)
+ return retval;
+ }
+
+ if (!adding && !deleting &&
+ cpumask_equal(trialcs->cpus_allowed, cs_reserve_cpus))
+ return 0;
+
+ /* Preserve trialcs->cpus_allowed for now */
+ init_tmpmasks(&tmp, NULL, trialcs->subparts_cpus,
+ trialcs->effective_cpus);
+
+ /*
+ * Compute the addition and removal of CPUs to/from cs_reserve_cpus
+ */
+ if (!adding && !deleting) {
+ adding = cpumask_andnot(tmp.addmask, trialcs->cpus_allowed,
+ cs_reserve_cpus);
+ deleting = cpumask_andnot(tmp.delmask, cs_reserve_cpus,
+ trialcs->cpus_allowed);
+ } else if (adding) {
+ adding = cpumask_andnot(tmp.addmask,
+ trialcs->cpus_allowed, cs_reserve_cpus);
+ cpumask_or(trialcs->cpus_allowed, cs_reserve_cpus, tmp.addmask);
+ } else { /* deleting */
+ deleting = cpumask_and(tmp.delmask,
+ trialcs->cpus_allowed, cs_reserve_cpus);
+ cpumask_andnot(trialcs->cpus_allowed, cs_reserve_cpus, tmp.delmask);
+ }
+
+ if (!adding && !deleting)
+ return 0;
+
+ /*
+ * Invalidate remote partitions if necessary
+ */
+ if (deleting) {
+ /* TODO */
+ }
+
+ /*
+ * Cannot use up all the CPUs in top_cpuset.effective_cpus
+ */
+ if (!deleting && adding &&
+ cpumask_subset(top_cpuset.effective_cpus, tmp.addmask))
+ return -EINVAL;
+
+ spin_lock_irq(&callback_lock);
+ /*
+ * Update top_cpuset.effective_cpus, cs_reserve_cpus &
+ * cs_free_reserve_cpus.
+ */
+ if (adding)
+ cpumask_or(cs_free_reserve_cpus, cs_free_reserve_cpus,
+ tmp.addmask);
+ cpumask_copy(cs_reserve_cpus, trialcs->cpus_allowed);
+ cpumask_andnot(top_cpuset.effective_cpus,
+ cpu_active_mask, cs_reserve_cpus);
+
+ /*
+ * Remove CPUs from cs_free_reserve_cpus first. Anything left
+ * means some partitions has to be made invalid.
+ */
+ if (deleting & cpumask_and(cs_tmp_cpus, cs_free_reserve_cpus,
+ tmp.delmask)) {
+ cpumask_andnot(cs_free_reserve_cpus, cs_free_reserve_cpus,
+ cs_tmp_cpus);
+ deleting = cpumask_andnot(tmp.delmask, tmp.delmask,
+ cs_tmp_cpus);
+ }
+ spin_unlock_irq(&callback_lock);
+
+ /*
+ * Invalidate some adjacent partitions under top cpuset, if necessary
+ */
+ if (deleting && cpumask_and(cs_tmp_cpus, tmp.delmask,
+ top_cpuset.subparts_cpus)) {
+ struct cgroup_subsys_state *css;
+ struct cpuset *cp;
+
+ /*
+ * Temporarily save the remaining CPUs to be deleted in
+ * trialcs->cpus_allowed to be restored back to tmp.delmask
+ * later.
+ */
+ deleting = cpumask_andnot(trialcs->cpus_allowed, tmp.delmask,
+ cs_tmp_cpus);
+ rcu_read_lock();
+ cpuset_for_each_child(cp, css, &top_cpuset)
+ if (is_partition_valid(cp) &&
+ cpumask_intersects(cs_tmp_cpus, cp->cpus_allowed)) {
+ rcu_read_unlock();
+ update_parent_subparts_cpumask(cp, partcmd_invalidate, NULL, &tmp);
+ rcu_read_lock();
+ }
+ rcu_read_unlock();
+ if (deleting)
+ cpumask_copy(tmp.delmask, trialcs->cpus_allowed);
+ }
+
+ /* Can now use all of trialcs */
+ init_tmpmasks(&tmp, trialcs->cpus_allowed, trialcs->subparts_cpus,
+ trialcs->effective_cpus);
+
+ /*
+ * Update effective_cpus of all descendants that are not in
+ * partitions and rebuild sched domaiins.
+ */
+ rcu_read_lock();
+ cpuset_for_each_child(cs, css, &top_cpuset) {
+ compute_effective_cpumask(tmp.new_cpus, cs, &top_cpuset);
+ if (cpumask_equal(tmp.new_cpus, cs->effective_cpus))
+ continue;
+ if (!css_tryget_online(&cs->css))
+ continue;
+ rcu_read_unlock();
+ update_cpumasks_hier(cs, &tmp, false);
+ rcu_read_lock();
+ css_put(&cs->css);
+ }
+ rcu_read_unlock();
+ rebuild_sched_domains_locked();
+ return 0;
+}
+
/*
* Migrate memory region from one set of nodes to another. This is
* performed asynchronously as it can be called from process migration path
@@ -2743,6 +2948,7 @@ typedef enum {
FILE_EFFECTIVE_CPULIST,
FILE_EFFECTIVE_MEMLIST,
FILE_SUBPARTS_CPULIST,
+ FILE_RESERVE_CPULIST,
FILE_CPU_EXCLUSIVE,
FILE_MEM_EXCLUSIVE,
FILE_MEM_HARDWALL,
@@ -2880,6 +3086,9 @@ static ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
case FILE_CPULIST:
retval = update_cpumask(cs, trialcs, buf);
break;
+ case FILE_RESERVE_CPULIST:
+ retval = update_reserve_cpumask(trialcs, buf);
+ break;
case FILE_MEMLIST:
retval = update_nodemask(cs, trialcs, buf);
break;
@@ -2927,6 +3136,9 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
case FILE_EFFECTIVE_MEMLIST:
seq_printf(sf, "%*pbl\n", nodemask_pr_args(&cs->effective_mems));
break;
+ case FILE_RESERVE_CPULIST:
+ seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs_reserve_cpus));
+ break;
case FILE_SUBPARTS_CPULIST:
seq_printf(sf, "%*pbl\n", cpumask_pr_args(cs->subparts_cpus));
break;
@@ -3200,6 +3412,14 @@ static struct cftype dfl_files[] = {
.file_offset = offsetof(struct cpuset, partition_file),
},
+ {
+ .name = "cpus.reserve",
+ .seq_show = cpuset_common_seq_show,
+ .write = cpuset_write_resmask,
+ .private = FILE_RESERVE_CPULIST,
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ },
+
{
.name = "cpus.subpartitions",
.seq_show = cpuset_common_seq_show,
@@ -3510,6 +3730,8 @@ int __init cpuset_init(void)
BUG_ON(!alloc_cpumask_var(&top_cpuset.effective_cpus, GFP_KERNEL));
BUG_ON(!zalloc_cpumask_var(&top_cpuset.subparts_cpus, GFP_KERNEL));
BUG_ON(!zalloc_cpumask_var(&cs_tmp_cpus, GFP_KERNEL));
+ BUG_ON(!zalloc_cpumask_var(&cs_reserve_cpus, GFP_KERNEL));
+ BUG_ON(!zalloc_cpumask_var(&cs_free_reserve_cpus, GFP_KERNEL));
cpumask_setall(top_cpuset.cpus_allowed);
nodes_setall(top_cpuset.mems_allowed);
@@ -3788,10 +4010,10 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
/*
- * In the rare case that hotplug removes all the cpus in subparts_cpus,
+ * In the rare case that hotplug removes all the reserve cpus,
* we assumed that cpus are updated.
*/
- if (!cpus_updated && top_cpuset.nr_subparts_cpus)
+ if (!cpus_updated && !cpumask_empty(cs_reserve_cpus))
cpus_updated = true;
/* synchronize cpus_allowed to cpu_active_mask */
@@ -3801,18 +4023,21 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
/*
* Make sure that CPUs allocated to child partitions
- * do not show up in effective_cpus. If no CPU is left,
- * we clear the subparts_cpus & let the child partitions
- * fight for the CPUs again.
+ * do not show up in top_cpuset's effective_cpus. In the
+ * unlikely event tht no effective CPU is left in top_cpuset,
+ * we clear all the reserve cpus and let the non-remote child
+ * partitions fight for the CPUs again.
*/
- if (top_cpuset.nr_subparts_cpus) {
- if (cpumask_subset(&new_cpus,
- top_cpuset.subparts_cpus)) {
+ if (!cpumask_empty(cs_reserve_cpus)) {
+
+ if (cpumask_subset(&new_cpus, cs_reserve_cpus)) {
top_cpuset.nr_subparts_cpus = 0;
cpumask_clear(top_cpuset.subparts_cpus);
+ cpumask_clear(cs_free_reserve_cpus);
+ cpumask_clear(cs_reserve_cpus);
} else {
cpumask_andnot(&new_cpus, &new_cpus,
- top_cpuset.subparts_cpus);
+ cs_reserve_cpus);
}
}
cpumask_copy(top_cpuset.effective_cpus, &new_cpus);
--
2.31.1
