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SubjectRe: [RFC PATCH 2/4] SCHED_DEADLINE cpu heap code clarification/refactory.
Hi,

nice clean-up. Maybe change the subject to something like
"sched/deadline: refactor cpu heap code" ?

On 19/07/16 11:44, Tommaso Cucinotta wrote:

This change does two things:

> 1. heapify up factored out in new dedicated function heapify_up()
> (avoids repeatition of same code)

s/repeatition/repetition/

> 2. call to cpudl_change_key() replaced with heapify_up() when
> cpudl_set actually inserts a new node in the heap
>

Maybe we want a separate patch (we usually want 1 patch - 1 change) ?

> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@arm.com>
> Cc: Luca Abeni <luca.abeni@unitn.it>
> Reviewed-by: Luca Abeni <luca.abeni@unitn.it>
> Signed-off-by: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
> ---
> kernel/sched/cpudeadline.c | 38 +++++++++++++++++++-------------------
> 1 file changed, 19 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index d418449..3c42702 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -41,7 +41,7 @@ static void cpudl_exchange(struct cpudl *cp, int a, int b)
> swap(cp->elements[cpu_a].idx, cp->elements[cpu_b].idx);
> }
>
> -static void cpudl_heapify(struct cpudl *cp, int idx)
> +static void cpudl_heapify_down(struct cpudl *cp, int idx)
> {
> int l, r, largest;
>
> @@ -66,20 +66,25 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
> }
> }
>
> +static void cpudl_heapify_up(struct cpudl *cp, int idx)
> +{
> + while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
> + cp->elements[idx].dl)) {
> + cpudl_exchange(cp, idx, parent(idx));
> + idx = parent(idx);
> + }
> +}
> +
> static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
> {
> WARN_ON(idx == IDX_INVALID || !cpu_present(idx));
>
> if (dl_time_before(new_dl, cp->elements[idx].dl)) {
> cp->elements[idx].dl = new_dl;
> - cpudl_heapify(cp, idx);
> + cpudl_heapify_down(cp, idx);
> } else {
> cp->elements[idx].dl = new_dl;
> - while (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
> - cp->elements[idx].dl)) {
> - cpudl_exchange(cp, idx, parent(idx));
> - idx = parent(idx);
> - }
> + cpudl_heapify_up(cp, idx);
> }
> }
>
> @@ -154,24 +159,19 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
> cp->size--;
> cp->elements[new_cpu].idx = old_idx;
> cp->elements[cpu].idx = IDX_INVALID;
> - while (old_idx > 0 && dl_time_before(
> - cp->elements[parent(old_idx)].dl,
> - cp->elements[old_idx].dl)) {
> - cpudl_exchange(cp, old_idx, parent(old_idx));
> - old_idx = parent(old_idx);
> - }
> + cpudl_heapify_up(cp, old_idx);
> cpumask_set_cpu(cpu, cp->free_cpus);
> - cpudl_heapify(cp, old_idx);
> + cpudl_heapify_down(cp, old_idx);

I think this line was already whitespace damaged. Could you fix it (with
a proper tab) in next version?

>
> goto out;
> }
>
> if (old_idx == IDX_INVALID) {
> - cp->size++;
> - cp->elements[cp->size - 1].dl = dl;
> - cp->elements[cp->size - 1].cpu = cpu;
> - cp->elements[cpu].idx = cp->size - 1;
> - cpudl_change_key(cp, cp->size - 1, dl);
> + int size1 = cp->size++;

s/size1/new_size/ ?

> + cp->elements[size1].dl = dl;
> + cp->elements[size1].cpu = cpu;
> + cp->elements[cpu].idx = size1;
> + cpudl_heapify_up(cp, size1);
> cpumask_clear_cpu(cpu, cp->free_cpus);
> } else {
> cpudl_change_key(cp, old_idx, dl);

We also seem to do almost the same ("cp->size - 1" mutliple times and
then cp->size--) up above, !is_valid branch. Maybe we want to clean
that up as well?

Thanks,

- Juri

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