kthread: NUMA aware kthread_create_on_node()

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_node(), 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>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 27 insertions, 7 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index cbc6adc6e891..a8f64f8ec7e1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -40,6 +40,7 @@
 #include <linux/tracehook.h>
 #include <linux/futex.h>
 #include <linux/compat.h>
+#include <linux/kthread.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/rcupdate.h>
 #include <linux/ptrace.h>
@@ -254,7 +255,7 @@ 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 c55afba990a3..684ab3f7dd72 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 node;
 
         /* Result passed back to kthread_create() from kthreadd. */
         struct task_struct *result;
@@ -98,10 +99,23 @@ 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->node;
+#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 +125,18 @@ static void create_kthread(struct kthread_create_info *create)
 }
 
 /**
- * kthread_create - create a kthread.
+ * kthread_create_on_node - create a kthread.
  * @threadfn: the function to run until signal_pending(current).
  * @data: data ptr for @threadfn.
+ * @node: memory node 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 node
+ * in @node, 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 +146,17 @@ 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_node(int (*threadfn)(void *data),
+                                           void *data,
+                                           int node,
+                                           const char namefmt[],
+                                           ...)
 {
         struct kthread_create_info create;
 
         create.threadfn = threadfn;
         create.data = data;
+        create.node = node;
         init_completion(&create.done);
 
         spin_lock(&kthread_create_lock);
@@ -164,7 +183,7 @@ struct task_struct *kthread_create(int (*threadfn)(void *data),
         }
         return create.result;
 }
-EXPORT_SYMBOL(kthread_create);
+EXPORT_SYMBOL(kthread_create_on_node);
 
 /**
  * kthread_bind - bind a just-created kthread to a cpu.