linux-kernel - [PATCH 15/36] autonuma: alloc/free/init task

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Date:	Wed, 22 Aug 2012 16:58:59 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:	Hillf Danton <dhillf@...il.com>, Dan Smith <danms@...ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Alex Shi <alex.shi@...el.com>,
	Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Don Morris <don.morris@...com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: [PATCH 15/36] autonuma: alloc/free/init task_autonuma

This is where the dynamically allocated task_autonuma structure is
being handled.

This is the structure holding the per-thread NUMA statistics generated
by the NUMA hinting page faults. This per-thread NUMA statistical
information is needed by sched_autonuma_balance to make optimal NUMA
balancing decisions.

It also contains the task_selected_nid which hints the stock CPU
scheduler on the best NUMA node to schedule this thread on (as decided
by sched_autonuma_balance).

The reason for keeping this outside of the task_struct besides not
using too much kernel stack, is to only allocate it on NUMA
hardware. So the non NUMA hardware only pays the memory of a pointer
in the kernel stack (which remains NULL at all times in that case).

If the kernel is compiled with CONFIG_AUTONUMA=n, not even the pointer
is allocated on the kernel stack of course.

Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
---
 kernel/fork.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index fbc67ee..9ba6e9b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -209,6 +209,7 @@ void free_task(struct task_struct *tsk)
 {
 	account_kernel_stack(tsk->stack, -1);
 	arch_release_thread_info(tsk->stack);
+	free_task_autonuma(tsk);
 	free_thread_info(tsk->stack);
 	rt_mutex_debug_task_free(tsk);
 	ftrace_graph_exit_task(tsk);
@@ -264,6 +265,9 @@ void __init fork_init(unsigned long mempages)
 	/* do the arch specific task caches init */
 	arch_task_cache_init();
 
+	/* prepare task_autonuma for alloc_task_autonuma/free_task_autonuma */
+	task_autonuma_init();
+
 	/*
 	 * The default maximum number of threads is set to a safe
 	 * value: the thread structures can take up at most half
@@ -310,6 +314,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 	if (err)
 		goto free_ti;
 
+	if (unlikely(alloc_task_autonuma(tsk, orig, node)))
+		/* free_thread_info() undoes arch_dup_task_struct() too */
+		goto free_ti;
+
 	tsk->stack = ti;
 
 	setup_thread_stack(tsk, orig);
--
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