linux-kernel - Re: [PATCH 20/40] autonuma: alloc/free/init mm

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Message-ID: <20120630051217.GG3975@localhost.localdomain>
Date:	Sat, 30 Jun 2012 01:12:18 -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>,
	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: Re: [PATCH 20/40] autonuma: alloc/free/init mm_autonuma

On Thu, Jun 28, 2012 at 02:56:00PM +0200, Andrea Arcangeli wrote:
> This is where the mm_autonuma structure is being handled. Just like
> sched_autonuma, this is only allocated at runtime if the hardware the
> kernel is running on has been detected as NUMA. On not NUMA hardware

I think the correct wording is "non-NUMA", not "not NUMA".

> the memory cost is reduced to one pointer per mm.
> 
> To get rid of the pointer in the each mm, the kernel can be compiled
> with CONFIG_AUTONUMA=n.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
> ---
>  kernel/fork.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> 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;

So reading that I would think that on non-NUMA machines this would fail
(since there is nothing to allocate). But that is not the case
(I hope!?) Perhaps just make the function not return any values?

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