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[PATCH 4.4 17/30] kernek/fork.c: allocate idle task for a CPU always on its local node

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andi Kleen <ak@linux.intel.com>

commit 725fc629ff2545b061407305ae51016c9f928fce upstream.

Linux preallocates the task structs of the idle tasks for all possible
CPUs.  This currently means they all end up on node 0.  This also
implies that the cache line of MWAIT, which is around the flags field in
the task struct, are all located in node 0.

We see a noticeable performance improvement on Knights Landing CPUs when
the cache lines used for MWAIT are located in the local nodes of the
CPUs using them.  I would expect this to give a (likely slight)
improvement on other systems too.

The patch implements placing the idle task in the node of its CPUs, by
passing the right target node to copy_process()

[akpm@linux-foundation.org: use NUMA_NO_NODE, not a bare -1]
Link: http://lkml.kernel.org/r/1463492694-15833-1-git-send-email-andi@firstfloor.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/fork.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -331,13 +331,14 @@ void set_task_stack_end_magic(struct tas
 	*stackend = STACK_END_MAGIC;	/* for overflow detection */
 }
 
-static struct task_struct *dup_task_struct(struct task_struct *orig)
+static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 {
 	struct task_struct *tsk;
 	struct thread_info *ti;
-	int node = tsk_fork_get_node(orig);
 	int err;
 
+	if (node == NUMA_NO_NODE)
+		node = tsk_fork_get_node(orig);
 	tsk = alloc_task_struct_node(node);
 	if (!tsk)
 		return NULL;
@@ -1270,7 +1271,8 @@ static struct task_struct *copy_process(
 					int __user *child_tidptr,
 					struct pid *pid,
 					int trace,
-					unsigned long tls)
+					unsigned long tls,
+					int node)
 {
 	int retval;
 	struct task_struct *p;
@@ -1323,7 +1325,7 @@ static struct task_struct *copy_process(
 		goto fork_out;
 
 	retval = -ENOMEM;
-	p = dup_task_struct(current);
+	p = dup_task_struct(current, node);
 	if (!p)
 		goto fork_out;
 
@@ -1699,7 +1701,8 @@ static inline void init_idle_pids(struct
 struct task_struct *fork_idle(int cpu)
 {
 	struct task_struct *task;
-	task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0);
+	task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0,
+			    cpu_to_node(cpu));
 	if (!IS_ERR(task)) {
 		init_idle_pids(task->pids);
 		init_idle(task, cpu);
@@ -1744,7 +1747,7 @@ long _do_fork(unsigned long clone_flags,
 	}
 
 	p = copy_process(clone_flags, stack_start, stack_size,
-			 child_tidptr, NULL, trace, tls);
+			 child_tidptr, NULL, trace, tls, NUMA_NO_NODE);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.

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[PATCH 4.4 00/30] 4.4.57-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:10 +0100
  [PATCH 4.4 16/30] hv_netvsc: use skb_get_hash() instead of a homegrown implementation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 23/30] target/pscsi: Fix TYPE_TAPE + TYPE_MEDIMUM_CHANGER export Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 21/30] powerpc/boot: Fix zImage TOC alignment Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 12/30] KVM: PPC: Book3S PR: Fix illegal opcode emulation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 17/30] kernek/fork.c: allocate idle task for a CPU always on its local node Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 19/30] perf/core: Fix event inheritance on fork() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 01/30] usb: core: hub: hub_port_init lock controller instead of bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 22/30] md/raid1/10: fix potential deadlock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 02/30] USB: dont free bandwidth_mutex too early Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 13/30] s390/pci: fix use after free in dma_init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 15/30] tpm_tis: Use devm_free_irq not free_irq Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 24/30] scsi: lpfc: Add shutdown method for kexec Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  [PATCH 4.4 20/30] cpufreq: Fix and clean up show_cpuinfo_cur_freq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-24 19:20 +0100
  Re: [PATCH 4.4 00/30] 4.4.57-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-03-25 01:10 +0100
  Re: [PATCH 4.4 00/30] 4.4.57-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-25 05:20 +0100
  Re: [PATCH 4.4 00/30] 4.4.57-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-25 05:20 +0100
    Re: [PATCH 4.4 00/30] 4.4.57-stable review Alexandre Belloni <alexandre.belloni@free-electrons.com> - 2017-03-25 12:30 +0100
      Re: [PATCH 4.4 00/30] 4.4.57-stable review Alexandre Belloni <alexandre.belloni@free-electrons.com> - 2017-03-25 12:40 +0100

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