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Date: Wed, 15 Jan 2014 10:58:29 +0400
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To: Christian Seiler <chris_se@gmx.net>
Cc: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] New Memory Manager
From: dmitry@zend.com (Dmitry Stogov)

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Hi Christian,

It's a clear solution, but indirect call may cause a lot of branch
miss-predictions, so it needs to be tested if it can improve performance.
binary compatibility is going to be broken anyway, so it's not a problem.

Thanks. Dmitry.


On Tue, Jan 14, 2014 at 11:38 PM, Christian Seiler <chris_se@gmx.net> wrote:

> Hi there,
>
>
>  (For example: may be someone would
>> suggest how to avoid check for USE_ZEND_ALLOC=0 to allow system malloc()
>> usage on each emalloc() call?
>>
>
> Rename emalloc() -> real_emalloc(), then:
>
> .h:
> extern void (*emalloc)(size_t n);
>
> .c:
> void (*emalloc)(size_t n) = real_emalloc;
>
> startup code:
>
> if (USE_ZEND_ALLOC is 0) {
>   emalloc = malloc;
> }
>
> Probably some adjustments needed (esp. for potentially different calling
> conventions, so maybe malloc() will need a small wrapper), this is just
> from the top of my head.
>
> Note: this breaks ABI compatibility on most archs (because it changes
> the symbol type). But could be done independently of anything else.
>
> Note 2: Depending on system architecture, each call to the function may
> incur an additional (small) penalty. No idea how this compares to the
> penalty of the if() at the start of emalloc().
>
> Regards,
> Christian
>
>

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