lkml.org 
[lkml]   [2013]   [Aug]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/4] mm, rmap: do easy-job first in anon_vma_fork
On Tue, Aug 06, 2013 at 05:43:37PM +0900, Joonsoo Kim wrote:
> If we fail due to some errorous situation, it is better to quit
> without doing heavy work. So changing order of execution.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index a149e3a..c2f51cb 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -278,19 +278,19 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
> if (!pvma->anon_vma)
> return 0;
>
> + /* First, allocate required objects */
> + avc = anon_vma_chain_alloc(GFP_KERNEL);
> + if (!avc)
> + goto out_error;
> + anon_vma = anon_vma_alloc();
> + if (!anon_vma)
> + goto out_error_free_avc;
> +
> /*
> - * First, attach the new VMA to the parent VMA's anon_vmas,
> + * Then attach the new VMA to the parent VMA's anon_vmas,
> * so rmap can find non-COWed pages in child processes.
> */
> if (anon_vma_clone(vma, pvma))
> - return -ENOMEM;
> -
> - /* Then add our own anon_vma. */
> - anon_vma = anon_vma_alloc();
> - if (!anon_vma)
> - goto out_error;
> - avc = anon_vma_chain_alloc(GFP_KERNEL);
> - if (!avc)
> goto out_error_free_anon_vma;

Which heavy work? anon_vma_clone() is anon_vma_chain_alloc() in a
loop.

Optimizing error paths only makes sense if they are common and you
actually could save something by reordering. This matches neither.


\
 
 \ /
  Last update: 2013-08-06 15:21    [W:0.107 / U:9.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site