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From: Kent Overstreet <kent.overstreet@linux.dev>
To: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: colyli@suse.de, bfoster@redhat.com, jserv@ccns.ncku.edu.tw,
	 linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-bcachefs@vger.kernel.org
Subject: Re: [PATCH 0/5] Optimize number of comparisons for heap/heapsort implementaion
Date: Sun, 21 Jan 2024 12:41:55 -0500	[thread overview]
Message-ID: <ioyfizrzq7w7mjrqcadtzsfgpuntowtjdw5pgn4qhvsdp4mqqg@nrlek5vmisbu> (raw)
In-Reply-To: <Za1Ml/ZUBXdYXOIt@visitorckw-System-Product-Name>

On Mon, Jan 22, 2024 at 12:55:51AM +0800, Kuan-Wei Chiu wrote:
> On Sun, Jan 21, 2024 at 11:21:06AM -0500, Kent Overstreet wrote:
> > On Sun, Jan 21, 2024 at 11:36:44PM +0800, Kuan-Wei Chiu wrote:
> > > Hello,
> > > 
> > > The existing implementations of heap/heapsort follow the conventional
> > > textbook approach, where each heapify operation requires approximately
> > > 2*log2(n) comparisons. In this series, I introduce a bottom-up variant
> > > that reduces the number of comparisons during heapify operations to
> > > approximately log2(n), while maintaining the same number of swap
> > > operations.
> > > 
> > > Thanks,
> > > Kuan-Wei
> > > 
> > > Kuan-Wei Chiu (5):
> > >   bcachefs: Optimize eytzinger0_sort() using bottom-up heapsort
> > >   bcachefs: Introduce parent function for sort_cmp_size()
> > >   bcachefs: Optimize sort_cmp_size() using bottom-up heapsort
> > >   bcachefs: Optimize number of comparisons in heap_sift_down
> > >   bcache: Optimize number of comparisons in heap_sift
> > > 
> > >  drivers/md/bcache/util.h |  23 +++++----
> > >  fs/bcachefs/util.c       | 109 ++++++++++++++++++++++++++-------------
> > >  fs/bcachefs/util.h       |  23 +++++----
> > >  3 files changed, 98 insertions(+), 57 deletions(-)
> > 
> > Good stuff
> > 
> > While we're looking at this code, we should be doing some cleanup too -
> > there's no reason for the heap code to be duplicated in bcache and
> > bcachefs anymore, and it'd also be nice to get fs/bcachefs/eytzinger.h
> > moved to include/linux and bcache converted to use it.
> > 
> > I also would not be surprised if there's another heap implementation in
> > include/linux; we'll want to check for that and if there is decide which
> > is worth keeping.
> >
> Yes, we have 'min_heap.h' in include/linux.

So that has the advantage of more readable code - functions instead of
macros - whereas my version has the type safe interface.

We could combine the two approaches, and put a type-safe interface on
top of the min_heap.h code with some small macro wrappers - see
generic-radix-tree.h for an example of how that's done.

min_heap.h has only one user though? I don't think I can quite believe
that's the only other code in the kernel using a heap, there must be
more open coded out there...

  reply	other threads:[~2024-01-21 17:41 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-21 15:36 [PATCH 0/5] Optimize number of comparisons for heap/heapsort implementaion Kuan-Wei Chiu
2024-01-21 15:36 ` [PATCH 1/5] bcachefs: Optimize eytzinger0_sort() using bottom-up heapsort Kuan-Wei Chiu
2024-01-21 15:36 ` [PATCH 2/5] bcachefs: Introduce parent function for sort_cmp_size() Kuan-Wei Chiu
2024-01-21 16:17   ` Kent Overstreet
2024-01-21 17:05     ` Kuan-Wei Chiu
2024-01-21 17:37       ` Kent Overstreet
2024-01-21 15:36 ` [PATCH 3/5] bcachefs: Optimize sort_cmp_size() using bottom-up heapsort Kuan-Wei Chiu
2024-01-21 15:36 ` [PATCH 4/5] bcachefs: Optimize number of comparisons in heap_sift_down Kuan-Wei Chiu
2024-01-21 15:36 ` [PATCH 5/5] bcache: Optimize number of comparisons in heap_sift Kuan-Wei Chiu
2024-01-21 16:21 ` [PATCH 0/5] Optimize number of comparisons for heap/heapsort implementaion Kent Overstreet
2024-01-21 16:55   ` Kuan-Wei Chiu
2024-01-21 17:41     ` Kent Overstreet [this message]
2024-01-22 15:06       ` Kuan-Wei Chiu
2024-01-22 16:06         ` Kent Overstreet
2024-01-22 16:23           ` Kuan-Wei Chiu

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