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Date: Sun, 01 Jul 2012 11:33:17 -0400
From: Rik van Riel <riel@redhat.com>
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Subject: Re: [PATCH 20/40] autonuma: alloc/free/init mm_autonuma
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>, Suresh Siddha <suresh.b.siddha@intel.com>, Mike Galbraith <efault@gmx.de>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Lai Jiangshan <laijs@cn.fujitsu.com>, Bharata B Rao <bharata.rao@gmail.com>, Lee Schermerhorn <Lee.Schermerhorn@hp.com>, Johannes Weiner <hannes@cmpxchg.org>, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>, Christoph Lameter <cl@linux.com>, Alex Shi <alex.shi@intel.com>, Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Don Morris <don.morris@hp.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>

On 06/28/2012 08:56 AM, Andrea Arcangeli wrote:

> diff --git a/kernel/fork.c b/kernel/fork.c
> index 0adbe09..3e5a0d9 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -527,6 +527,8 @@ static void mm_init_aio(struct mm_struct *mm)
>
>   static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
>   {
> +	if (unlikely(alloc_mm_autonuma(mm)))
> +		goto out_free_mm;
>   	atomic_set(&mm->mm_users, 1);
>   	atomic_set(&mm->mm_count, 1);
>   	init_rwsem(&mm->mmap_sem);

I wonder if it would be possible to defer the allocation
of the mm_autonuma struct to knuma_scand, so short lived
processes never have to allocate and free the mm_autonuma
structure.

That way we only have a function call at exit time, and
the branch inside kfree that checks for a null pointer.

-- 
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