linux-kernel - Re: [PATCH 12/13] lib min_heap: Add min_heap_sift

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Date: Tue, 19 Mar 2024 13:12:18 -0700
From: Ian Rogers <irogers@...gle.com>
To: Kuan-Wei Chiu <visitorckw@...il.com>
Cc: colyli@...e.de, kent.overstreet@...ux.dev, msakai@...hat.com, 
	peterz@...radead.org, mingo@...hat.com, acme@...nel.org, namhyung@...nel.org, 
	akpm@...ux-foundation.org, bfoster@...hat.com, mark.rutland@....com, 
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org, adrian.hunter@...el.com, 
	jserv@...s.ncku.edu.tw, linux-bcache@...r.kernel.org, 
	dm-devel@...ts.linux.dev, linux-bcachefs@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/13] lib min_heap: Add min_heap_sift_up()

On Tue, Mar 19, 2024 at 11:01 AM Kuan-Wei Chiu <visitorckw@...il.com> wrote:
>
> Add min_heap_sift_up() to sift up the element at index 'idx' in the
> heap.

Normally sift up is used to implement the min heap but isn't part of
the API, eg. there is a sift up in min_heap_push. Should min_heapify
be renamed to min_heap_sift_down to align with this name?

Thanks,
Ian

> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>
> ---
>  include/linux/min_heap.h | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/include/linux/min_heap.h b/include/linux/min_heap.h
> index ce085137fce7..586965977104 100644
> --- a/include/linux/min_heap.h
> +++ b/include/linux/min_heap.h
> @@ -199,6 +199,26 @@ bool __min_heap_push(struct __min_heap *heap, const void *element, size_t elem_s
>  #define min_heap_push(_heap, _element, _func, _args)   \
>         __min_heap_push(&(_heap)->heap, _element, __minheap_obj_size(_heap), _func, _args)
>
> +/* Sift up ith element from the heap, O(log2(nr)). */
> +static __always_inline
> +void __min_heap_sift_up(struct __min_heap *heap, size_t elem_size, size_t idx,
> +               const struct min_heap_callbacks *func, void *args)
> +{
> +       void *data = heap->data;
> +       size_t parent;
> +
> +       while (idx) {
> +               parent = (idx - 1) / 2;
> +               if (func->less(data + parent * elem_size, data + idx * elem_size, args))
> +                       break;
> +               func->swp(data + parent * elem_size, data + idx * elem_size, args);
> +               idx = parent;
> +       }
> +}
> +
> +#define min_heap_sift_up(_heap, _idx, _func, _args)    \
> +       __min_heap_sift_up(&(_heap)->heap, __minheap_obj_size(_heap), _idx, _func, _args)
> +
>  /* Remove ith element from the heap, O(log2(nr)). */
>  static __always_inline
>  bool __min_heap_del(struct __min_heap *heap, size_t elem_size, size_t idx,
> --
> 2.34.1
>