lib: Restrict cpumask_local_spread to houskeeping CPUs (1abdfe70) · Commits · 戴 / test

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 <abelits@marvell.com> Signed-off-by:

Nitesh Narayan Lal <nitesh@redhat.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200625223443.2684-2-nitesh@redhat.com

lib/cpumask.c

+11 −5

Original line number	Diff line number	Diff line
		@@ -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;

Admin message