integ/kernel/kernel-rt/centos/patches/affine-compute-kernel-threads.patch

From a15588101329965ad3974bd571a9207d6a5e154a Mon Sep 17 00:00:00 2001
Message-Id: <a15588101329965ad3974bd571a9207d6a5e154a.1528226387.git.Jim.Somerville@windriver.com>
In-Reply-To: <c8270e79f6b7008fde44b8d5aa6314d8cf89d3ed.1528226387.git.Jim.Somerville@windriver.com>
References: <c8270e79f6b7008fde44b8d5aa6314d8cf89d3ed.1528226387.git.Jim.Somerville@windriver.com>
From: Chris Friesen <chris.friesen@windriver.com>
Date: Tue, 24 Nov 2015 16:27:28 -0500
Subject: [PATCH 04/32] affine compute kernel threads

This is a kernel enhancement to configure the cpu affinity of kernel
threads via kernel boot option kthread_cpus=<cpulist>. The compute
kickstart file and compute-huge.sh scripts will update grub with the
new option.

With kthread_cpus specified, the cpumask is immediately applied upon
thread launch. This does not affect kernel threads that specify cpu
and node.

Note: this is based off of 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: Christoph Lameter <cl@linux.com>
Signed-off-by: Chris Friesen <chris.friesen@windriver.com>
[VT: The existing "isolcpus"
 kernel bootarg, cgroup/cpuset, and taskset might provide the some
 way to have cpu isolation.  However none of them satisfies the requirements.
 Replacing spaces with tabs. Combine two calls of set_cpus_allowed_ptr()
 in kernel_init_freeable() in init/main.c into one.  Performed tests]
Signed-off-by: Vu Tran <vu.tran@windriver.com>

Signed-off-by: Jim Somerville <Jim.Somerville@windriver.com>
---
 Documentation/kernel-parameters.txt | 10 ++++++++++
 include/linux/cpumask.h             |  2 ++
 init/main.c                         |  6 ++----
 kernel/cpu.c                        | 13 +++++++++++++
 kernel/kmod.c                       |  3 +++
 kernel/kthread.c                    |  4 ++--
 6 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 02cfdf6..4eeda61 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1551,6 +1551,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	kpti		[X86-64] Enable kernel page table isolation.
 
+	kthread_cpus=	[KNL, SMP] Only run kernel threads on the specified
+			list of processors. The kernel will start threads
+			on the indicated processors only (unless there
+			are specific reasons to run a thread with
+			different affinities). This can be used to make
+			init start on certain processors and also to
+			control where kmod and other user space threads
+			are being spawned. Allows to keep kernel threads
+			away from certain cores unless absoluteluy necessary.
+
 	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
 			Default is 0 (don't ignore, but inject #GP)
 
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index ee335c6..46ae77a 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -52,6 +52,7 @@ extern int nr_cpu_ids;
  *     cpu_present_mask - has bit 'cpu' set iff cpu is populated
  *     cpu_online_mask  - has bit 'cpu' set iff cpu available to scheduler
  *     cpu_active_mask  - has bit 'cpu' set iff cpu available to migration
+ *     cpu_kthread_mask - has bit 'cpu' set iff general kernel threads allowed
  *
  *  If !CONFIG_HOTPLUG_CPU, present == possible, and active == online.
  *
@@ -88,6 +89,7 @@ extern const struct cpumask *const cpu_possible_mask;
 extern const struct cpumask *const cpu_online_mask;
 extern const struct cpumask *const cpu_present_mask;
 extern const struct cpumask *const cpu_active_mask;
+extern const struct cpumask *const cpu_kthread_mask;
 
 #if NR_CPUS > 1
 #define num_online_cpus()	cpumask_weight(cpu_online_mask)
diff --git a/init/main.c b/init/main.c
index 2e4ecd4..6e265d0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -961,10 +961,6 @@ static noinline void __init kernel_init_freeable(void)
 	 * init can allocate pages on any node
 	 */
 	set_mems_allowed(node_states[N_MEMORY]);
-	/*
-	 * init can run on any cpu.
-	 */
-	set_cpus_allowed_ptr(current, cpu_all_mask);
 
 	cad_pid = task_pid(current);
 
@@ -980,6 +976,8 @@ static noinline void __init kernel_init_freeable(void)
 
 	do_basic_setup();
 
+	set_cpus_allowed_ptr(current, cpu_kthread_mask);
+
 	/* Open the /dev/console on the rootfs, this should never fail */
 	if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
 		pr_err("Warning: unable to open an initial console.\n");
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6fe84e4..325a47a 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1329,6 +1329,19 @@ static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
 EXPORT_SYMBOL(cpu_active_mask);
 
+static DECLARE_BITMAP(cpu_kthread_bits, CONFIG_NR_CPUS) __read_mostly
+	= CPU_BITS_ALL;
+const struct cpumask *const cpu_kthread_mask = to_cpumask(cpu_kthread_bits);
+EXPORT_SYMBOL(cpu_kthread_mask);
+
+static int __init kthread_setup(char *str)
+{
+	cpulist_parse(str, (struct cpumask *)&cpu_kthread_bits);
+	return 1;
+}
+__setup("kthread_cpus=", kthread_setup);
+
+
 void set_cpu_possible(unsigned int cpu, bool possible)
 {
 	if (possible)
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 86ab754..4bf584b 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -204,6 +204,9 @@ static int ____call_usermodehelper(void *data)
 	flush_signal_handlers(current, 1);
 	spin_unlock_irq(&current->sighand->siglock);
 
+	/* We can run only where init is allowed to run. */
+	set_cpus_allowed_ptr(current, cpu_kthread_mask);
+
 	/*
 	 * Our parent is keventd, which runs with elevated scheduling priority.
 	 * Avoid propagating that into the userspace child.
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 703d910..7ea32eb 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -284,7 +284,7 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 		 * The kernel thread should not inherit these properties.
 		 */
 		sched_setscheduler_nocheck(create.result, SCHED_NORMAL, &param);
-		set_cpus_allowed_ptr(create.result, cpu_all_mask);
+		set_cpus_allowed_ptr(create.result, cpu_kthread_mask);
 	}
 	return create.result;
 }
@@ -454,7 +454,7 @@ 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_all_mask);
+	set_cpus_allowed_ptr(tsk, cpu_kthread_mask);
 	set_mems_allowed(node_states[N_MEMORY]);
 
 	current->flags |= PF_NOFREEZE;
-- 
1.8.3.1