Hello Xin,
On Fri, 22 Oct 2021 00:44:16 +0800 Xin Hao <xhao@xxxxxxxxxxxxxxxxx> wrote:
> When we want to clear previously set target ids,
> For example, it works as below now:
> # echo 42 > target_ids
> # cat target_ids
> 42
> # echo > target_ids
> # cat target_ids
>
> But in 'dbgfs_target_ids_write', there is no need to
> execute other codes, except call 'damon_set_targets'
> to clear previously set target ids. So there adds
> the 'nr_targets' judgment, if the value is 0, just
> call 'damon_set_targets', and then return.
It's true that it executes some unnecessary code. However, I unsure if that is
a problem, as the code that will be additionally executed in this case are
quite simple ones, and therefore not supposed to incur viewable overhead.
After all, this is not a performance critical path.
Thanks,
SJ
>
> Signed-off-by: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
> ---
> mm/damon/dbgfs.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
> index a02cf6bee8e8..1d83f4138fad 100644
> --- a/mm/damon/dbgfs.c
> +++ b/mm/damon/dbgfs.c
> @@ -362,6 +362,12 @@ static ssize_t dbgfs_target_ids_write(struct file *file,
> goto out;
> }
>
> + if (!nr_targets) {
> + /* remove targets with previously-set primitive */
> + damon_set_targets(ctx, NULL, 0);
> + goto free_targets_out;
> + }
> +
> if (id_is_pid) {
> for (i = 0; i < nr_targets; i++) {
> targets[i] = (unsigned long)find_get_pid(
> --
> 2.31.0
