linux-kernel - Re: [PATCH 2/2] radix-tree: Fix optimisation problem

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Message-ID: <CALXu0UdXLt0Lccqnx2TMSgK1Or0whKLRuF-+rXuzqmkhYksgSQ@mail.gmail.com>
Date:   Sun, 25 Sep 2016 21:40:58 +0200
From:   Cedric Blancher <cedric.blancher@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Matthew Wilcox <mawilcox@...uxonhyperv.com>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>
Subject: Re: [PATCH 2/2] radix-tree: Fix optimisation problem

LGTM, except that #define is_sibling_entry should be IS_SIBLING_ENTRY

Ced

On 25 September 2016 at 21:04, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Sun, Sep 25, 2016 at 11:04 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> The more I look at that particular piece of code, the less I like it. It's
>> buggy shit. It needs to be rewritten entirely too actually check for sibling
>> entries, not that ad-hoc arithmetic crap.
>
> Here's my attempt at cleaning the mess up.
>
> I'm not claiming it's perfect, but I think it's better. It gets rid of
> the ad-hoc arithmetic in radix_tree_descend(), and just makes all that
> be inside the is_sibling_entry() logic instead. Which got renamed and
> made to actually return the main sibling. So now there is at least
> only *one* piece of code that does that range comparison, and I don't
> think there is any huge need to explain what's going on, because the
> "magic" is unconditional.
>
> Willy?
>
>                  Linus



-- 
Cedric Blancher <cedric.blancher@...il.com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur