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cgroup/cpuset: Allow suppression of sched domain rebuild in update_cpumasks_hier() 

A single partition setup and tear-down operation can lead to
multiple rebuild_sched_domains_locked() calls which is a waste of
effort. This can partly be mitigated by adding a flag to suppress the
rebuild_sched_domains_locked() call in update_cpumasks_hier(). Since
a Boolean flag has already been passed as the 3rd argument to
update_cpumasks_hier(), we can extend that to a full flag word.

The sched domain rebuild suppression is now enabled in
update_sibling_cpumasks() as all it callers will do the sched domain
rebuild after its return later on anyway.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2023-06-27 10:35:03 -04:00 committed by Tejun Heo
parent 99fe36ba6f
commit 3ae0b77321
1 changed files with 16 additions and 8 deletions
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24
kernel/cgroup/cpuset.c
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@ -1590,6 +1590,12 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
return 0; return 0;
} }
/*
* update_cpumasks_hier() flags
*/
#define HIER_CHECKALL 0x01 /* Check all cpusets with no skipping */
#define HIER_NO_SD_REBUILD 0x02 /* Don't rebuild sched domains */
/* /*
* update_cpumasks_hier - Update effective cpumasks and tasks in the subtree * update_cpumasks_hier - Update effective cpumasks and tasks in the subtree
* @cs: the cpuset to consider * @cs: the cpuset to consider
@ -1604,7 +1610,7 @@ static int update_parent_subparts_cpumask(struct cpuset *cs, int cmd,
* Called with cpuset_mutex held * Called with cpuset_mutex held
*/ */
static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp, static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
bool force) int flags)
{ {
struct cpuset *cp; struct cpuset *cp;
struct cgroup_subsys_state *pos_css; struct cgroup_subsys_state *pos_css;
@ -1644,10 +1650,10 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
* Skip the whole subtree if * Skip the whole subtree if
* 1) the cpumask remains the same, * 1) the cpumask remains the same,
* 2) has no partition root state, * 2) has no partition root state,
* 3) force flag not set, and * 3) HIER_CHECKALL flag not set, and
* 4) for v2 load balance state same as its parent. * 4) for v2 load balance state same as its parent.
*/ */
if (!cp->partition_root_state && !force && if (!cp->partition_root_state && !(flags & HIER_CHECKALL) &&
cpumask_equal(tmp->new_cpus, cp->effective_cpus) && cpumask_equal(tmp->new_cpus, cp->effective_cpus) &&
(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) || (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
(is_sched_load_balance(parent) == is_sched_load_balance(cp)))) { (is_sched_load_balance(parent) == is_sched_load_balance(cp)))) {
@ -1764,7 +1770,7 @@ update_parent_subparts:
} }
rcu_read_unlock(); rcu_read_unlock();
if (need_rebuild_sched_domains) if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD))
rebuild_sched_domains_locked(); rebuild_sched_domains_locked();
} }
@ -1788,7 +1794,9 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
* to use the right effective_cpus value. * to use the right effective_cpus value.
* *
* The update_cpumasks_hier() function may sleep. So we have to * The update_cpumasks_hier() function may sleep. So we have to
* release the RCU read lock before calling it. * release the RCU read lock before calling it. HIER_NO_SD_REBUILD
* flag is used to suppress rebuild of sched domains as the callers
* will take care of that.
*/ */
rcu_read_lock(); rcu_read_lock();
cpuset_for_each_child(sibling, pos_css, parent) { cpuset_for_each_child(sibling, pos_css, parent) {
@ -1800,7 +1808,7 @@ static void update_sibling_cpumasks(struct cpuset *parent, struct cpuset *cs,
continue; continue;
rcu_read_unlock(); rcu_read_unlock();
update_cpumasks_hier(sibling, tmp, false); update_cpumasks_hier(sibling, tmp, HIER_NO_SD_REBUILD);
rcu_read_lock(); rcu_read_lock();
css_put(&sibling->css); css_put(&sibling->css);
} }
@ -1913,7 +1921,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
spin_unlock_irq(&callback_lock); spin_unlock_irq(&callback_lock);
/* effective_cpus will be updated here */ /* effective_cpus will be updated here */
update_cpumasks_hier(cs, &tmp, false); update_cpumasks_hier(cs, &tmp, 0);
if (cs->partition_root_state) { if (cs->partition_root_state) {
struct cpuset *parent = parent_cs(cs); struct cpuset *parent = parent_cs(cs);
@ -2382,7 +2390,7 @@ out:
* Force update if switching back to member. * Force update if switching back to member.
*/ */
if (!list_empty(&cs->css.children)) if (!list_empty(&cs->css.children))
update_cpumasks_hier(cs, &tmpmask, !new_prs); update_cpumasks_hier(cs, &tmpmask, !new_prs ? HIER_CHECKALL : 0);
/* Update sched domains and load balance flag */ /* Update sched domains and load balance flag */
update_partition_sd_lb(cs, old_prs); update_partition_sd_lb(cs, old_prs);