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@xxxxxxxxxx>
---
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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