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

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Date: Wed, 20 Mar 2024 10:51:51 +0800
From: Kuan-Wei Chiu <visitorckw@...il.com>
To: Ian Rogers <irogers@...gle.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 01:12:18PM -0700, Ian Rogers wrote:
> 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?
> 

Sure, I can add a patch in v2 to rename min_heapify to min_heap_sift_down.

Regards,
Kuan-Wei

> 
> > 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
> >