isolcpus: Affine unbound kernel threads to housekeeping cpus (9cc5b865) · Commits · 戴 / test

This is a kernel enhancement that configures the cpu affinity of kernel threads via kernel boot option nohz_full=. When this option is specified, the cpumask is immediately applied upon kthread launch. This does not affect kernel threads that specify cpu and node. This allows CPU isolation (that is not allowing certain threads to execute on certain CPUs) without using the isolcpus=domain parameter, making it possible to enable load balancing on such CPUs during runtime (see kernel-parameters.txt). Note-1: this is based off on Wind River's patch at https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch Difference being that this patch is limited to modifying kernel thread cpumask. Behaviour of other threads can be controlled via cgroups or sched_setaffinity. Note-2: Wind River's patch was based off Christoph Lameter's patch at https://lwn.net/Articles/565932/ with the only difference being the kernel parameter changed from kthread to kthread_cpus. Signed-off-by:

Frederic Weisbecker <frederic@kernel.org> Signed-off-by:

Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200527142909.23372-3-frederic@kernel.org

include/linux/sched/isolation.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -14,6 +14,7 @@ enum hk_flags {
		HK_FLAG_DOMAIN = (1 << 5),
		HK_FLAG_WQ = (1 << 6),
		HK_FLAG_MANAGED_IRQ = (1 << 7),
		HK_FLAG_KTHREAD = (1 << 8),
		};

		#ifdef CONFIG_CPU_ISOLATION

kernel/kthread.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -27,6 +27,7 @@
		#include <linux/ptrace.h>
		#include <linux/uaccess.h>
		#include <linux/numa.h>
		#include <linux/sched/isolation.h>
		#include <trace/events/sched.h>


		@@ -383,7 +384,8 @@ struct task_struct __kthread_create_on_node(int (threadfn)(void *data),
		* The kernel thread should not inherit these properties.
		*/
		sched_setscheduler_nocheck(task, SCHED_NORMAL, &param);
		set_cpus_allowed_ptr(task, cpu_possible_mask);
		set_cpus_allowed_ptr(task,
		housekeeping_cpumask(HK_FLAG_KTHREAD));
		}
		kfree(create);
		return task;
		@@ -608,7 +610,7 @@ int kthreadd(void *unused)
		/* Setup a clean context for our children to inherit. */
		set_task_comm(tsk, "kthreadd");
		ignore_signals(tsk);
		set_cpus_allowed_ptr(tsk, cpu_possible_mask);
		set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_FLAG_KTHREAD));
		set_mems_allowed(node_states[N_MEMORY]);

		current->flags \|= PF_NOFREEZE;

kernel/sched/isolation.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -140,7 +140,8 @@ static int __init housekeeping_nohz_full_setup(char *str)
		{
		unsigned int flags;

		flags = HK_FLAG_TICK \| HK_FLAG_WQ \| HK_FLAG_TIMER \| HK_FLAG_RCU \| HK_FLAG_MISC;
		flags = HK_FLAG_TICK \| HK_FLAG_WQ \| HK_FLAG_TIMER \| HK_FLAG_RCU \|
		HK_FLAG_MISC \| HK_FLAG_KTHREAD;

		return housekeeping_setup(str, flags);
		}

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