linux-kernel - Re: [PATCH v3 02/10] lib: introduce generic min max heap

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Message-ID: <20191114093501.GN4131@hirez.programming.kicks-ass.net>
Date:   Thu, 14 Nov 2019 10:35:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Petr Mladek <pmladek@...e.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Qian Cai <cai@....pw>, Joe Lawrence <joe.lawrence@...hat.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Changbin Du <changbin.du@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Gary Hook <Gary.Hook@....com>, Arnd Bergmann <arnd@...db.de>,
        Kan Liang <kan.liang@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v3 02/10] lib: introduce generic min max heap

On Wed, Nov 13, 2019 at 04:30:34PM -0800, Ian Rogers wrote:
> +/*
> + * Remove the minimum element and then push the given element. The
> + * implementation performs 1 sift (O(log2(size))) and is therefore more
> + * efficient than a pop followed by a push that does 2.
> + */
> +static void heap_pop_push(struct min_max_heap *heap,
> +			const void *element,
> +			const struct min_max_heap_callbacks *func)
> +{
> +	char *data = (char *)heap->data;
> +
> +	memcpy(data, element, func->elem_size);
> +	heapify(heap, 0, func);
> +}

I'm not a fan of this operation. It has a weird name and it is utterly
trivial.