linux-kernel - Re: [PATCH 18/35] autonuma: alloc/free/init sched

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Date:	Wed, 30 May 2012 16:55:24 -0400
From:	Konrad Rzeszutek Wilk <konrad@...nok.org>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Hillf Danton <dhillf@...il.com>, Dan Smith <danms@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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>
Subject: Re: [PATCH 18/35] autonuma: alloc/free/init sched_autonuma

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@...hat.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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