Re: [PATCH 18/35] autonuma: alloc/free/init sched_autonuma

Konrad Rzeszutek Wilk
2012-05-30T20:55:30Z

On Fri, May 25, 2012 at 07:02:22PM +0200, Andrea Arcangeli wrote:
> This is where the dynamically allocated sched_autonuma structure is
> being handled.
>
> 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 not 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@redhat.com>
> ---
> kernel/fork.c | 24 ++++++++++++++----------
> 1 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 237c34e..d323eb1 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -206,6 +206,7 @@ static void account_kernel_stack(struct thread_info *ti, int account)
> void free_task(struct task_struct *tsk)
> {
> account_kernel_stack(tsk->stack, -1);
> + free_sched_autonuma(tsk);
> free_thread_info(tsk->stack);
> rt_mutex_debug_task_free(tsk);
> ftrace_graph_exit_task(tsk);
> @@ -260,6 +261,8 @@ void __init fork_init(unsigned long mempages)
> /* do the arch specific task caches init */
> arch_task_cache_init();
>
> + sched_autonuma_init();
> +
> /*
> * The default maximum number of threads is set to a safe
> * value: the thread structures can take up at most half
> @@ -292,21 +295,21 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
> struct thread_info *ti;
> unsigned long *stackend;
> int node = tsk_fork_get_node(orig);
> - int err;
>
> tsk = alloc_task_struct_node(node);
> - if (!tsk)
> + if (unlikely(!tsk))
> return NULL;
>
> ti = alloc_thread_info_node(tsk, node);
> - if (!ti) {
> - free_task_struct(tsk);
> - return NULL;
> - }
> + if (unlikely(!ti))

Should those "unlikely" have their own commit? Did you
run this with the likely/unlikely tracer to confirm that it
does give a sppedup?

> + goto out_task_struct;
>
> - err = arch_dup_task_struct(tsk, orig);
> - if (err)
> - goto out;
> + if (unlikely(arch_dup_task_struct(tsk, orig)))
> + goto out_thread_info;
> +
> + if (unlikely(alloc_sched_autonuma(tsk, orig, node)))
> + /* free_thread_info() undoes arch_dup_task_struct() too */
> + goto out_thread_info;
>
> tsk->stack = ti;
>
> @@ -334,8 +337,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
>
> return tsk;
>
> -out:
> +out_thread_info:
> free_thread_info(ti);
> +out_task_struct:
> free_task_struct(tsk);
> return NULL;
> }
>
> --
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