linux-kernel - Re: [PATCH 13/19] s390: get rid of superfluous __GFP

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Date:	Mon, 11 Apr 2016 13:28:37 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	<linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-arch@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 13/19] s390: get rid of superfluous __GFP_REPEAT

On Mon, 11 Apr 2016 13:08:06 +0200
Michal Hocko <mhocko@...nel.org> wrote:

> From: Michal Hocko <mhocko@...e.com>
> 
> __GFP_REPEAT has a rather weak semantic but since it has been introduced
> around 2.6.12 it has been ignored for low order allocations.
> 
> arch_dup_task_struct uses __GFP_REPEAT for fpu_regs_size which is either
> sizeof(__vector128) * __NUM_VXRS = 4069B resp.
> sizeof(freg_t) * __NUM_FPRS = 1024B AFAICS. page_table_alloc then uses
> the flag for a single page allocation. This means that this flag has
> never been actually useful here because it has always been used only for
> PAGE_ALLOC_COSTLY requests.
> 
> Cc: Christian Borntraeger <borntraeger@...ibm.com>
> Cc: Cornelia Huck <cornelia.huck@...ibm.com>

Let's cc: Martin/Heiko instead :)

> Cc: linux-arch@...r.kernel.org
> Signed-off-by: Michal Hocko <mhocko@...e.com>
> ---
>  arch/s390/kernel/process.c | 2 +-
>  arch/s390/mm/pgalloc.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
> index f8e79824e284..1837a1901d4b 100644
> --- a/arch/s390/kernel/process.c
> +++ b/arch/s390/kernel/process.c
> @@ -102,7 +102,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>  	 */
>  	fpu_regs_size = MACHINE_HAS_VX ? sizeof(__vector128) * __NUM_VXRS
>  				       : sizeof(freg_t) * __NUM_FPRS;
> -	dst->thread.fpu.regs = kzalloc(fpu_regs_size, GFP_KERNEL|__GFP_REPEAT);
> +	dst->thread.fpu.regs = kzalloc(fpu_regs_size, GFP_KERNEL);
>  	if (!dst->thread.fpu.regs)
>  		return -ENOMEM;
> 
> diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c
> index f6c3de26cda8..3f716741797a 100644
> --- a/arch/s390/mm/pgalloc.c
> +++ b/arch/s390/mm/pgalloc.c
> @@ -198,7 +198,7 @@ unsigned long *page_table_alloc(struct mm_struct *mm)
>  			return table;
>  	}
>  	/* Allocate a fresh page */
> -	page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
> +	page = alloc_page(GFP_KERNEL);
>  	if (!page)
>  		return NULL;
>  	if (!pgtable_page_ctor(page)) {