linux-kernel - Re: [PATCH] exec: remove page_table_lock for mm counters in acct_arg

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Date:	Thu, 14 Jul 2011 15:18:22 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Frantisek Hrbata <fhrbata@...hat.com>
Cc:	linux-kernel@...r.kernel.org, matt.fleming@...ux.intel.com,
	hughd@...gle.com
Subject: Re: [PATCH] exec: remove page_table_lock for mm counters in
	acct_arg_size()

On 07/14, Frantisek Hrbata wrote:
>
> Commit 172703b mm: delete non-atomic mm counter implementation
> removed non-atomic mm counters implementation. I think there is no need to hold
> page_table_lock for add_mm_counter() when the splitted page table locks are not
> used. This patch removes the locking.
>
> Signed-off-by: Frantisek Hrbata <fhrbata@...hat.com>
> ---
>  fs/exec.c |    6 ------
>  1 files changed, 0 insertions(+), 6 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index 6075a1e..e6fc5e1 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -182,13 +182,7 @@ static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>
>  	bprm->vma_pages = pages;
>
> -#ifdef SPLIT_RSS_COUNTING
>  	add_mm_counter(mm, MM_ANONPAGES, diff);
> -#else
> -	spin_lock(&mm->page_table_lock);
> -	add_mm_counter(mm, MM_ANONPAGES, diff);
> -	spin_unlock(&mm->page_table_lock);
> -#endif

Heh. Thanks Frantisek, you are right. But this patch is already in mm-tree,
fs-execc-acct_arg_size-ptl-is-no-longer-needed-for-add_mm_counter.patch

Oleg.

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