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authorRik van Riel <riel@redhat.com>2015-03-09 12:12:08 -0400
committerTejun Heo <tj@kernel.org>2015-03-19 14:28:19 -0400
commit47b8ea7186aae7f474ec4c98f43eaa8da719cd83 (patch)
tree5c6d1dc3e08e9816fd6ab746c25e0edd01271fdf
parent3fa0818b3c85e9bb55e3ac96c9523b87e44eab9e (diff)
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cpusets, isolcpus: exclude isolcpus from load balancing in cpusets
Ensure that cpus specified with the isolcpus= boot commandline option stay outside of the load balancing in the kernel scheduler. Operations like load balancing can introduce unwanted latencies, which is exactly what the isolcpus= commandline is there to prevent. Previously, simply creating a new cpuset, without even touching the cpuset.cpus field inside the new cpuset, would undo the effects of isolcpus=, by creating a scheduler domain spanning the whole system, and setting up load balancing inside that domain. The cpuset root cpuset.cpus file is read-only, so there was not even a way to undo that effect. This does not impact the majority of cpusets users, since isolcpus= is a fairly specialized feature used for realtime purposes. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Clark Williams <williams@redhat.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: cgroups@vger.kernel.org Signed-off-by: Rik van Riel <riel@redhat.com> Tested-by: David Rientjes <rientjes@google.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/cpuset.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index fc7f4748d34a..c68f0721df10 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -622,6 +622,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
int csn; /* how many cpuset ptrs in csa so far */
int i, j, k; /* indices for partition finding loops */
cpumask_var_t *doms; /* resulting partition; i.e. sched domains */
+ cpumask_var_t non_isolated_cpus; /* load balanced CPUs */
struct sched_domain_attr *dattr; /* attributes for custom domains */
int ndoms = 0; /* number of sched domains in result */
int nslot; /* next empty doms[] struct cpumask slot */
@@ -631,6 +632,10 @@ static int generate_sched_domains(cpumask_var_t **domains,
dattr = NULL;
csa = NULL;
+ if (!alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL))
+ goto done;
+ cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
+
/* Special case for the 99% of systems with one, full, sched domain */
if (is_sched_load_balance(&top_cpuset)) {
ndoms = 1;
@@ -643,7 +648,8 @@ 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.effective_cpus);
+ cpumask_and(doms[0], top_cpuset.effective_cpus,
+ non_isolated_cpus);
goto done;
}
@@ -666,7 +672,8 @@ static int generate_sched_domains(cpumask_var_t **domains,
* the corresponding sched domain.
*/
if (!cpumask_empty(cp->cpus_allowed) &&
- !is_sched_load_balance(cp))
+ !(is_sched_load_balance(cp) &&
+ cpumask_intersects(cp->cpus_allowed, non_isolated_cpus)))
continue;
if (is_sched_load_balance(cp))
@@ -748,6 +755,7 @@ restart:
if (apn == b->pn) {
cpumask_or(dp, dp, b->effective_cpus);
+ cpumask_and(dp, dp, non_isolated_cpus);
if (dattr)
update_domain_attr_tree(dattr + nslot, b);
@@ -760,6 +768,7 @@ restart:
BUG_ON(nslot != ndoms);
done:
+ free_cpumask_var(non_isolated_cpus);
kfree(csa);
/*