| Message ID | 1fbada4f02475f69abbccd105c92dc3512dd6ab0.1513591276.git.christophe.leroy@c-s.fr |
|---|---|
| State | New |
| Headers | show |
| Series | [1/4] gpio: sysfs: change 'value' attribute to prealloc | expand |
On Mon, Dec 18, 2017 at 11:08 AM, Christophe Leroy <christophe.leroy@c-s.fr> wrote: > A bench with 'perf record' shows that most of time spent in value_show() > is spent in sprintf() > > --42.41%--sysfs_kf_read > | > |--39.73%--dev_attr_show > | | > | |--38.23%--value_show > | | | > | | |--29.22%--sprintf > | | | > | | |--2.94%--gpiod_get_value_cansleep > | | | > > value_show() only returns "0\n" or "1\n", therefore the use of > sprintf() can be avoided > > With this patch we get the following result with 'perf record' > > --13.89%--sysfs_kf_read > | > |--10.72%--dev_attr_show > | | > | |--9.44%--value_show > | | | > | | |--4.61%--gpiod_get_value_cansleep > > Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Patch applied. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c index 1b0f415df03b..bb10e8ed456e 100644 --- a/drivers/gpio/gpiolib-sysfs.c +++ b/drivers/gpio/gpiolib-sysfs.c @@ -110,7 +110,9 @@ static ssize_t value_show(struct device *dev, if (status < 0) goto err; - status = sprintf(buf, "%d\n", status); + buf[0] = '0' + status; + buf[1] = '\n'; + status = 2; err: mutex_unlock(&data->mutex);
A bench with 'perf record' shows that most of time spent in value_show() is spent in sprintf() --42.41%--sysfs_kf_read | |--39.73%--dev_attr_show | | | |--38.23%--value_show | | | | | |--29.22%--sprintf | | | | | |--2.94%--gpiod_get_value_cansleep | | | value_show() only returns "0\n" or "1\n", therefore the use of sprintf() can be avoided With this patch we get the following result with 'perf record' --13.89%--sysfs_kf_read | |--10.72%--dev_attr_show | | | |--9.44%--value_show | | | | | |--4.61%--gpiod_get_value_cansleep Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> --- drivers/gpio/gpiolib-sysfs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)