[Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs
From: Nitesh Narayan Lal <hidden>
Date: 2020-06-25 22:39:32
Also in:
linux-api, lkml
Subsystem:
bitmap api, library code, the rest · Maintainers:
Yury Norov, Andrew Morton, Linus Torvalds
From: Alex Belits <redacted> 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: Alex Belits <redacted> Signed-off-by: Nitesh Narayan Lal <redacted> --- lib/cpumask.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/lib/cpumask.c b/lib/cpumask.c
index fb22fb266f93..85da6ab4fbb5 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c@@ -6,6 +6,7 @@ #include <linux/export.h> #include <linux/memblock.h> #include <linux/numa.h> +#include <linux/sched/isolation.h> /** * cpumask_next - get the next cpu in a cpumask
@@ -205,22 +206,27 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask) */ 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. */ - i %= num_online_cpus(); + i %= cpumask_weight(mask); if (node == NUMA_NO_NODE) { - for_each_cpu(cpu, cpu_online_mask) + for_each_cpu(cpu, mask) { if (i-- == 0) return cpu; + } } else { /* 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) return cpu; + } - for_each_cpu(cpu, cpu_online_mask) { + for_each_cpu(cpu, mask) { /* Skip NUMA nodes, done above. */ if (cpumask_test_cpu(cpu, cpumask_of_node(node))) continue;
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2.18.4