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From: Crt Mori <cmo@melexis.com>
Date: Wed, 20 Dec 2017 17:17:29 +0100
Message-ID: <CAKv63uuL9+xzF7KruhYwSY68-M0=aJSvJOr5Y0vVBiX8ebqfeg@mail.gmail.com>
Subject: Re: [PATCH v10 1/3] lib: Add strongly typed 64bit int_sqrt
To: Peter Zijlstra <peterz@infradead.org>
Cc: David Laight <David.Laight@aculab.com>,
        Jonathan Cameron <jic23@kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Rusty Russell <rusty@rustcorp.com.au>, Ian Abbott <abbotti@mev.co.uk>,
        Larry Finger <Larry.Finger@lwfinger.net>,
        Niklas Soderlund <niklas.soderlund+renesas@ragnatech.se>,
        Thomas Gleixner <tglx@linutronix.de>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        Joe Perches <joe@perches.com>
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On 20 December 2017 at 17:00, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Dec 20, 2017 at 02:39:26PM +0000, David Laight wrote:
>
>> With minor changes it ought to be possible to remove most of the
>> 64bit arithmetic and shifts.
>>
>> If you care about performance then using 32 bit maths will be much faster.
>
> Some, u64 add/sub/shift isn't exactly expensive, but yes, I also
> indicated that improvement is possible. At the very least y can be made
> a u32 I suppose.

OK, is there any more easy optimizations you see?