lkml.org 
[lkml]   [2011]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: One comment on the __release_region in kernel/resource.c
On Sun, 2 Oct 2011 21:57:07 +0800
Wei Yang <weiyang.kernel@gmail.com> wrote:

> Dear experts,
>
> I am viewing the source code of __release_region() in kernel/resource.c.
> And I have one comment for the performance issue.
>
> For example, we have a resource tree like this.
> 10-89
> 20-79
> 30-49
> 55-59
> 60-64
> 65-69
> 80-89
> 100-279
>
> If the caller wants to release a region of [50,59], the original code will
> execute four times in the for loop in the subtree of 20-79.
>
> After changing the code below, it will execute two times instead.
>
> By using the "git annotate", I see this code is committed by Linus as the
> initial version. So don't get more information about why this code is
> written
> in this way.
>
> Maybe the case I thought will not happen in the real world?
>
> Your comment is warmly welcome. :)
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 8461aea..81525b4 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -931,7 +931,7 @@ void __release_region(struct resource *parent,
> resource_size_t start,
> for (;;) {
> struct resource *res = *p;
>
> - if (!res)
> + if (!res || res->start > start)

Hmm ?
res->start > end ?


Thanks,
-Kame



\
 
 \ /
  Last update: 2011-10-03 12:27    [W:0.049 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site