cpusets, isolcpus: exclude isolcpus from load balancing in cpusets (47b8ea71) · Commits · 戴 / test

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>

kernel/cpuset.c

+11 −2

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

		/*

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