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Date: Fri, 24 Jan 2014 15:29:48 +0400
Message-ID: <CA+9eiLsOJ5a6kcFpKt0DRzaem7Hi24sy7m=uSWDFMcvuMhiNAg@mail.gmail.com>
To: Anatol Belski <ab@php.net>
Cc: Pierre Joye <pierre.php@gmail.com>, Andrea Faulds <ajf@ajf.me>, Derick Rethans <derick@php.net>, 
	PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b5d35defe62f804f0b5ac02
Subject: Re: [PHP-DEV] [RFC] 64 bit platform improvements for string length
 and integer
From: dmitry@zend.com (Dmitry Stogov)

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Content-Type: text/plain; charset=UTF-8

I would be glad t see any 64-bit performance related improvements.

BTW: the performance degradation is expected. Each pointer is 64-bit
instead of 32-bit => more memory consumption => more CPU cache pressure =>
more CPU cache misses.

On the other hand x86-64 uses more CPU registers, MMX, SSE, passes
arguments in registers, so it's usually faster on small tasks that keep
working set in CPU caches.

Thanks. Dmitry.


On Fri, Jan 24, 2014 at 12:36 PM, Anatol Belski <ab@php.net> wrote:

> Hi Dmitry,
>
> On Fri, January 24, 2014 08:32, Dmitry Stogov wrote:
> > Unfortunately, my benchmarks on Linux show that 64-bit PHP builds are
> > always a bit slower on real-life applications. It's because 64-bit PHP
> uses
> > more memory and as result causes more CPU cache misses.
> >
> i suppose the perf test on windows to be done today.
>
> That topic was also it my mind while worked on str_size_and_int64 branch.
> What I have seen is that till now PHP code doesn't really care about 64
> bit performance. I was reading the "Software Optimization Guide for AMD64
> Processors" http://support.amd.com/TechDocs/25112.PDF and comparing with
> their recomendations one can find many places in PHP code needing some
> refactoring. Some primitive points to name like use of non contiguous
> values in switches, 32 bit vars in loops, no homogeneous 64 bit vars
> usage, etc. - could be improved. One of good moves is usage of the const
> qualifier lately. Now with the consistent 64 bit support such a
> refactoring would have base and sense.
>
> Regards
>
> Anatol
>

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