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Date: Thu, 14 Jan 2010 12:48:18 +0100
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To: Rasmus Lerdorf <rasmus@lerdorf.com>
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Subject: Re: [PHP-DEV] About optimization
From: php@hristov.com (Andrey Hristov)

Rasmus Lerdorf wrote:
> Tim Starling wrote:
>> <?php
>> class C {
>>     var $v1, $v2, $v3, $v4, $v5, $v6, $v7, $v8, $v9, $v10;
>> }
>>
>> $m = memory_get_usage();
>> $a = array();
>> for ( $i = 0; $i < 10000; $i++ ) {
>>     $a[] = new C;
>> }
>> print ((memory_get_usage() - $m) / 10000) . "\n";
>> ?>
>>
>> 1927 bytes (I'll use 64-bit from now on since it gives the most shocking
>> numbers)
> 
> PHP 5.3.3-dev (cli) (built: Jan 11 2010 11:26:25)
> Linux colo 2.6.31-1-amd64 #1 SMP Sat Oct 24 17:50:31 UTC 2009 x86_64
> 
> php > class C {
> php {     var $v1, $v2, $v3, $v4, $v5, $v6, $v7, $v8, $v9, $v10;
> php { }
> php >
> php > $m = memory_get_usage();
> php > $a = array();
> php > for ( $i = 0; $i < 10000; $i++ ) {
> php {     $a[] = new C;
> php { }
> php > print ((memory_get_usage() - $m) / 10000) . "\n";
> 1479.5632
> 
> So you need 1500 bytes per object in your array.  I still fail to see
> the problem for a web request.  Maybe I am just old-fashioned in the way
> I look at this stuff, but if you have more than 1000 objects loaded on a
> single request, you are doing something wrong as far as I am concerned.
> 
> This is why we do things like unbuffered mysql queries, zero-copy stream
> passing, etc.  We never want entire result sets or entire files in
> memory because even if we optimize the crap out of it, it is still going
> to be way faster to simply not do that.

actually with mysqlnd a buffered set might be faster, if you know what 
are you doing, because the data won't be copied once more. with 
unbuffered sets data is copied from the network buffer to the zval. With 
buffered sets the zval just pointes to the network buffer. If you have 
the RAM then buffered should be faster. Of course you should use the set 
and when finished close it and not fetch-close-process, because then 
copy is forced.

Best,
Andrey