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sched/numa: Init numa balancing fields of init_task

PATCH New Kirill Tkhai 2 participants 2 messages Nov 11, 2014 – Nov 16, 2014

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Kirill Tkhai

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#0 lore raw

PATCH 1/1 sched/numa: Init numa balancing fields of init_task

We do not initialize init_task.numa_preferred_nid, but this value is inherited by userspace "init" process:

rest_init()->kernel_thread(kernel_init)->do_fork(CLONE_VM);

__sched_fork()

{
	if (clone_flags & CLONE_VM)
		p->numa_preferred_nid = current->numa_preferred_nid;
	else
		p->numa_preferred_nid = -1;
}

kernel_init() becomes userspace "init" process.

So, we propagate garbage nid to userspace, and it may be used during numa balancing.

Currently, we do not have reports about this brings a problem, but it seem we should set it for sure.

Even if init_task.numa_preferred_nid is zero, we may meet a weird configuration without nid#0. On sparc64, where processors are numbered physically, I saw a machine without cpu#1, while cpu#2 existed. Possible, something similar may be with numa nodes. So, let's initialize it and be sure we're safe.

Signed-off-by Kirill Tkhai <[email protected]>
---
 include/linux/init_task.h |   10 ++++++++++
 1 file changed, 10 insertions(+)
include/linux/init_task.h +10 -0
index 77fc43f..5f30ac8 100644
@@ -166,6 +166,15 @@ extern struct task_group root_task_group;
 # define INIT_RT_MUTEXES(tsk)
 #endif
 
+#ifdef CONFIG_NUMA_BALANCING
+# define INIT_NUMA_BALANCING(tsk)					\
+	.numa_preferred_nid = -1,					\
+	.numa_group = NULL,						\
+	.numa_faults = NULL,
+#else
+# define INIT_NUMA_BALANCING(tsk)
+#endif
+
 /*
  *  INIT_TASK is used to set up the first task table, touch at
  * your own risk!. Base=0, limit=0x1fffff (=2MB)

@@ -237,6 +246,7 @@ extern struct task_group root_task_group;
 	INIT_CPUSET_SEQ(tsk)						\
 	INIT_RT_MUTEXES(tsk)						\
 	INIT_VTIME(tsk)							\
+	INIT_NUMA_BALANCING(tsk)					\
 }
merge bot
#1 lore raw
sched/numa: Init numa balancing fields of init_task
Commit-ID:  d8b163c4c657478ef33c082cff78d03a4ca07bb2
Gitweb:     http://git.kernel.org/tip/d8b163c4c657478ef33c082cff78d03a4ca07bb2
Author:     Kirill Tkhai <[email protected]>
AuthorDate: Tue, 11 Nov 2014 12:46:29 +0300
Committer:  Ingo Molnar <[email protected]>
CommitDate: Sun, 16 Nov 2014 10:59:01 +0100

sched/numa: Init numa balancing fields of init_task

We do not initialize init_task.numa_preferred_nid, but this value is inherited by userspace "init" process:

rest_init()->kernel_thread(kernel_init)->do_fork(CLONE_VM);

__sched_fork()

{
	if (clone_flags & CLONE_VM)
		p->numa_preferred_nid = current->numa_preferred_nid;
	else
		p->numa_preferred_nid = -1;
}

kernel_init() becomes userspace "init" process.

So, we propagate garbage nid to userspace, and it may be used during numa balancing.

Currently, we do not have reports about this brings a problem, but it seem we should set it for sure.

Even if init_task.numa_preferred_nid is zero, we may meet a weird configuration without nid#0. On sparc64, where processors are numbered physically, I saw a machine without cpu#1, while cpu#2 existed. Possible, something similar may be with numa nodes. So, let's initialize it and be sure we're safe.

Signed-off-by Kirill Tkhai <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Cc Eric Paris <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Oleg Nesterov <[email protected]>
Cc Paul E. McKenney <[email protected]>
Cc Sergey Dyasly <[email protected]>
Link http://lkml.kernel.org/r/1415699189.15631.6.camel@tkhai open here
Signed-off-by Ingo Molnar <[email protected]>
---
 include/linux/init_task.h | 10 ++++++++++
 1 file changed, 10 insertions(+)
include/linux/init_task.h +10 -0
index 77fc43f..5f30ac8 100644
@@ -166,6 +166,15 @@ extern struct task_group root_task_group;
 # define INIT_RT_MUTEXES(tsk)
 #endif
 
+#ifdef CONFIG_NUMA_BALANCING
+# define INIT_NUMA_BALANCING(tsk)					\
+	.numa_preferred_nid = -1,					\
+	.numa_group = NULL,						\
+	.numa_faults = NULL,
+#else
+# define INIT_NUMA_BALANCING(tsk)
+#endif
+
 /*
  *  INIT_TASK is used to set up the first task table, touch at
  * your own risk!. Base=0, limit=0x1fffff (=2MB)

@@ -237,6 +246,7 @@ extern struct task_group root_task_group;
 	INIT_CPUSET_SEQ(tsk)						\
 	INIT_RT_MUTEXES(tsk)						\
 	INIT_VTIME(tsk)							\
+	INIT_NUMA_BALANCING(tsk)					\
 }