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Date: Wed, 12 Feb 2014 17:11:21 +0900
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To: Lester Caine <lester@lsces.co.uk>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a1134d7aea4a23e04f23120bb
Subject: Re: [PHP-DEV] [VOTE] Timing attack safe string comparison function
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Hi all,

On Wed, Feb 12, 2014 at 4:24 PM, Lester Caine <lester@lsces.co.uk> wrote:

> Yasuo Ohgaki wrote:
>
>> We cannot assume word aligned data for strings. This is the reason why
>> there is
>> additional byte by byte comparison. It could be made to align memory to
>> word size,
>> but it requires memory allocation for comparison. I'm not sure which is
>> better, though.
>>
>
> Since PHP is controlling the memory management, there is no reason it
> can't properly align data elements ... based on the target platform. When
> you only had 640k of memory every byte counted, but these days the speed
> gain provided by simply wasting a few bytes and always padding buffers to a
> relevant word boundary is far greater than the space saving. Things have
> changed somewhat since the original C compilers were written. But this is
> better discussed on the 32/64bit optimization thread. Suffice to say that
> Firebird recorded substantial speed improvement once the basic ground rules
> were accepted and unnecessary 'byte related' processing dropped.


Word aligned memory allocation can be done. It may be good for
fragmentation also.
I don't read current memory manager code, so I cannot answer this.

Anyone?

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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