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Subject[PATCH v2 3/4] kthread: NUMA aware kthread_create_on_cpu()
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All kthreads being created from a single helper task, they all use
memory from a single node for their kernel stack and task struct.

This patch suite creates kthread_create_on_cpu(), adding a 'cpu'
parameter to parameters already used by kthread_create().

This parameter serves in allocating memory for the new kthread on its
memory node if possible.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: linux-arch@vger.kernel.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
---
include/linux/kthread.h | 14 ++++++++++----
include/linux/sched.h | 1 +
kernel/fork.c | 3 ++-
kernel/kthread.c | 32 ++++++++++++++++++++++++++------
4 files changed, 39 insertions(+), 11 deletions(-)
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 685ea65..ad753bc 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -4,10 +4,15 @@
#include <linux/err.h>
#include <linux/sched.h>

-struct task_struct *kthread_create(int (*threadfn)(void *data),
- void *data,
- const char namefmt[], ...)
- __attribute__((format(printf, 3, 4)));
+struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+ void *data,
+ int cpu,
+ const char namefmt[], ...)
+ __attribute__((format(printf, 4, 5)));
+
+#define kthread_create(threadfn, data, namefmt, arg...) \
+ kthread_create_on_cpu(threadfn, data, -1, namefmt, ##arg)
+

/**
* kthread_run - create and wake a thread.
@@ -34,6 +39,7 @@ void *kthread_data(struct task_struct *k);

int kthreadd(void *unused);
extern struct task_struct *kthreadd_task;
+extern int tsk_fork_get_node(struct task_struct *tsk);

/*
* Simple work processor based on kthread.
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2c79e92..e212776 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1456,6 +1456,7 @@ struct task_struct {
#ifdef CONFIG_NUMA
struct mempolicy *mempolicy; /* Protected by alloc_lock */
short il_next;
+ short pref_node_fork;
#endif
atomic_t fs_excl; /* holding fs exclusive resources */
struct rcu_head rcu;
diff --git a/kernel/fork.c b/kernel/fork.c
index 3ebae16..4355dd4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -66,6 +66,7 @@
#include <linux/posix-timers.h>
#include <linux/user-return-notifier.h>
#include <linux/oom.h>
+#include <linux/kthread.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -251,7 +252,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
struct task_struct *tsk;
struct thread_info *ti;
unsigned long *stackend;
- int node = numa_node_id();
+ int node = tsk_fork_get_node(orig);
int err;

prepare_to_copy(orig);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 2dc3786..4aec26d 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -27,6 +27,7 @@ struct kthread_create_info
/* Information passed to kthread() from kthreadd. */
int (*threadfn)(void *data);
void *data;
+ int cpu;

/* Result passed back to kthread_create() from kthreadd. */
struct task_struct *result;
@@ -98,10 +99,24 @@ static int kthread(void *_create)
do_exit(ret);
}

+/* called from do_fork() to get node information for about to be created task */
+int tsk_fork_get_node(struct task_struct *tsk)
+{
+#ifdef CONFIG_NUMA
+ if (tsk == kthreadd_task)
+ return tsk->pref_node_fork;
+#endif
+ return numa_node_id();
+}
+
static void create_kthread(struct kthread_create_info *create)
{
int pid;

+#ifdef CONFIG_NUMA
+ current->pref_node_fork = (create->cpu != -1) ?
+ cpu_to_node(create->cpu) : -1;
+#endif
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
@@ -111,15 +126,18 @@ static void create_kthread(struct kthread_create_info *create)
}

/**
- * kthread_create - create a kthread.
+ * kthread_create_on_cpu - create a kthread.
* @threadfn: the function to run until signal_pending(current).
* @data: data ptr for @threadfn.
+ * @cpu: cpu number.
* @namefmt: printf-style name for the thread.
*
* Description: This helper function creates and names a kernel
* thread. The thread will be stopped: use wake_up_process() to start
* it. See also kthread_run().
*
+ * If thread is going to be bound on a particular cpu, give its number
+ * in @cpu, to get NUMA affinity for kthread stack, or else give -1.
* When woken, the thread will run @threadfn() with @data as its
* argument. @threadfn() can either call do_exit() directly if it is a
* standalone thread for which noone will call kthread_stop(), or
@@ -129,15 +147,17 @@ static void create_kthread(struct kthread_create_info *create)
*
* Returns a task_struct or ERR_PTR(-ENOMEM).
*/
-struct task_struct *kthread_create(int (*threadfn)(void *data),
- void *data,
- const char namefmt[],
- ...)
+struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
+ void *data,
+ int cpu,
+ const char namefmt[],
+ ...)
{
struct kthread_create_info create;

create.threadfn = threadfn;
create.data = data;
+ create.cpu = cpu;
init_completion(&create.done);

spin_lock(&kthread_create_lock);
@@ -164,7 +184,7 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
}
return create.result;
}
-EXPORT_SYMBOL(kthread_create);
+EXPORT_SYMBOL(kthread_create_on_cpu);

/**
* kthread_bind - bind a just-created kthread to a cpu.



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