Commit 8b5f1c52 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo

cpuset: use effective cpumask to build sched domains

We're going to have separate user-configured masks and effective ones.

Eventually configured masks can only be changed by writing cpuset.cpus
and cpuset.mems, and they won't be restricted by parent cpuset. While
effective masks reflect cpu/memory hotplug and hierachical restriction,
and these are the real masks that apply to the tasks in the cpuset.

We calculate effective mask this way:
  - top cpuset's effective_mask == online_mask, otherwise
  - cpuset's effective_mask == configured_mask & parent effective_mask,
    if the result is empty, it inherits parent effective mask.

Those behavior changes are for default hierarchy only. For legacy
hierarchy, effective_mask and configured_mask are the same, so we won't
break old interfaces.

We should partition sched domains according to effective_cpus, which
is the real cpulist that takes effects on tasks in the cpuset.

This won't introduce behavior change.

- Add a comment for the call of rebuild_sched_domains(), suggested
by Tejun.
Signed-off-by: default avatarLi Zefan <>
Signed-off-by: default avatarTejun Heo <>
parent 554b0d1c
......@@ -494,11 +494,11 @@ out:
* Helper routine for generate_sched_domains().
* Do cpusets a, b have overlapping cpus_allowed masks?
* Do cpusets a, b have overlapping effective cpus_allowed masks?
static int cpusets_overlap(struct cpuset *a, struct cpuset *b)
return cpumask_intersects(a->cpus_allowed, b->cpus_allowed);
return cpumask_intersects(a->effective_cpus, b->effective_cpus);
static void
......@@ -615,7 +615,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
*dattr = SD_ATTR_INIT;
update_domain_attr_tree(dattr, &top_cpuset);
cpumask_copy(doms[0], top_cpuset.cpus_allowed);
cpumask_copy(doms[0], top_cpuset.effective_cpus);
goto done;
......@@ -719,7 +719,7 @@ restart:
struct cpuset *b = csa[j];
if (apn == b->pn) {
cpumask_or(dp, dp, b->cpus_allowed);
cpumask_or(dp, dp, b->effective_cpus);
if (dattr)
update_domain_attr_tree(dattr + nslot, b);
......@@ -771,7 +771,7 @@ static void rebuild_sched_domains_locked(void)
* passing doms with offlined cpu to partition_sched_domains().
* Anyways, hotplug work item will rebuild sched domains.
if (!cpumask_equal(top_cpuset.cpus_allowed, cpu_active_mask))
if (!cpumask_equal(top_cpuset.effective_cpus, cpu_active_mask))
goto out;
/* Generate domain masks and attrs */
......@@ -870,6 +870,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
struct cpuset *cp;
struct cgroup_subsys_state *pos_css;
bool need_rebuild_sched_domains = false;
cpuset_for_each_descendant_pre(cp, pos_css, cs) {
......@@ -903,10 +904,21 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
* If the effective cpumask of any non-empty cpuset is changed,
* we need to rebuild sched domains.
if (!cpumask_empty(cp->cpus_allowed) &&
need_rebuild_sched_domains = true;
if (need_rebuild_sched_domains)
......@@ -919,7 +931,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
const char *buf)
int retval;
int is_load_balanced;
/* top_cpuset.cpus_allowed tracks cpu_online_mask; it's read-only */
if (cs == &top_cpuset)
......@@ -950,17 +961,12 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
if (retval < 0)
return retval;
is_load_balanced = is_sched_load_balance(trialcs);
cpumask_copy(cs->cpus_allowed, trialcs->cpus_allowed);
/* use trialcs->cpus_allowed as a temp variable */
update_cpumasks_hier(cs, trialcs->cpus_allowed);
if (is_load_balanced)
return 0;
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