Re: [PATCH 4/9] select: Micro-optimise __estimate_accuracy()

Cyrill Gorcunov
2019-09-19T14:05:53Z

On Mon, Sep 09, 2019 at 11:23:35AM +0100, Dmitry Safonov wrote:
> Shift on s64 is faster than division, use it instead.
>
> As the result of the patch there is a hardly user-visible effect:
> poll(), select(), etc syscalls will be a bit more precise on ~2.3%
> than before because 1000 != 1024 :)
>
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> ---
> fs/select.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/fs/select.c b/fs/select.c
> index 12cdefd3be2d..2477c202631e 100644
> --- a/fs/select.c
> +++ b/fs/select.c
> @@ -51,15 +51,14 @@
>
> static long __estimate_accuracy(ktime_t slack)
> {
> - int divfactor = 1000;
> -
> if (slack < 0)
> return 0;

Btw, don't you better use <= here?