Commit 1abdfe70 authored by Alex Belits's avatar Alex Belits Committed by Peter Zijlstra

lib: Restrict cpumask_local_spread to houskeeping CPUs

The current implementation of cpumask_local_spread() does not respect the
isolated CPUs, i.e., even if a CPU has been isolated for Real-Time task,
it will return it to the caller for pinning of its IRQ threads. Having
these unwanted IRQ threads on an isolated CPU adds up to a latency
overhead.

Restrict the CPUs that are returned for spreading IRQs only to the
available housekeeping CPUs.
Signed-off-by: default avatarAlex Belits <abelits@marvell.com>
Signed-off-by: default avatarNitesh Narayan Lal <nitesh@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200625223443.2684-2-nitesh@redhat.com
parent 46609ce2
...@@ -6,6 +6,7 @@ ...@@ -6,6 +6,7 @@
#include <linux/export.h> #include <linux/export.h>
#include <linux/memblock.h> #include <linux/memblock.h>
#include <linux/numa.h> #include <linux/numa.h>
#include <linux/sched/isolation.h>
/** /**
* cpumask_next - get the next cpu in a cpumask * cpumask_next - get the next cpu in a cpumask
...@@ -205,22 +206,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) ...@@ -205,22 +206,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
*/ */
unsigned int cpumask_local_spread(unsigned int i, int node) unsigned int cpumask_local_spread(unsigned int i, int node)
{ {
int cpu; int cpu, hk_flags;
const struct cpumask *mask;
hk_flags = HK_FLAG_DOMAIN | HK_FLAG_MANAGED_IRQ;
mask = housekeeping_cpumask(hk_flags);
/* Wrap: we always want a cpu. */ /* Wrap: we always want a cpu. */
i %= num_online_cpus(); i %= cpumask_weight(mask);
if (node == NUMA_NO_NODE) { if (node == NUMA_NO_NODE) {
for_each_cpu(cpu, cpu_online_mask) for_each_cpu(cpu, mask) {
if (i-- == 0) if (i-- == 0)
return cpu; return cpu;
}
} else { } else {
/* NUMA first. */ /* NUMA first. */
for_each_cpu_and(cpu, cpumask_of_node(node), cpu_online_mask) for_each_cpu_and(cpu, cpumask_of_node(node), mask) {
if (i-- == 0) if (i-- == 0)
return cpu; return cpu;
}
for_each_cpu(cpu, cpu_online_mask) { for_each_cpu(cpu, mask) {
/* Skip NUMA nodes, done above. */ /* Skip NUMA nodes, done above. */
if (cpumask_test_cpu(cpu, cpumask_of_node(node))) if (cpumask_test_cpu(cpu, cpumask_of_node(node)))
continue; continue;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment