lkml.org 
[lkml]   [2017]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 4/4] gpio: sysfs: avoid using kstrtol() in 'value' attribute write
On Mon, Dec 18, 2017 at 11:08 AM, Christophe Leroy
<christophe.leroy@c-s.fr> wrote:

> A 'perf record' on an app continuously writing in the 'value'
> attribute show that most of the time is spent in kstrtol()
>
> --17.99%--value_store
> |
> |--10.17%--kstrtoint
> | |
> | |--8.82%--kstrtoll
> |
> |--2.50%--gpiod_set_value_cansleep
> |
> |--1.82%--u16_gpio_set
> |
> |--1.46%--value_store
>
> The normal case is to write 0 or 1 in the attribute, therefore
> this patch avoids the call to kstrtol() in the most common cases
>
> Then 'perf record' shows
>
> --7.21%--value_store
> |
> |--2.69%--u16_gpio_set
> |
> |--1.47%--value_store
> |
> |--1.08%--gpiod_set_value_cansleep
> |
> |--0.60%--mutex_lock
> |
> --0.58%--mutex_unlock
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>

Patch applied.

Yours,
Linus Walleij

\
 
 \ /
  Last update: 2017-12-20 10:35    [W:0.131 / U:0.232 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site