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Date: Thu, 15 Apr 2010 09:14:16 +0200
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To: =?UTF-8?B?SsOpcsO0bWUgTG95ZXQ=?= <jerome@loyet.net>
Cc: =?UTF-8?B?5ruV6Lev6YGl?= <tly.phpfans@gmail.com>, 
	Rasmus Lerdorf <rasmus@lerdorf.com>, internals@lists.php.net
Content-Type: multipart/alternative; boundary=0015175cd5e414b18d0484413e29
Subject: Re: [PHP-DEV] One suggestion to PHP-FPM
From: tyra3l@gmail.com (Ferenc Kovacs)

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On Thu, Apr 15, 2010 at 9:09 AM, Ferenc Kovacs <tyra3l@gmail.com> wrote:

>
>
> 2010/4/15 J=C3=A9r=C3=B4me Loyet <jerome@loyet.net>
>
> 2010/4/15 =E6=BB=95=E8=B7=AF=E9=81=A5 <tly.phpfans@gmail.com>:
>> > We check error log after our server crashed, and we found that php hea=
p
>> > memory is out of limit,
>> > so I think imagick use emalloc to allocate php heap memory, to check t=
he
>> > zend_memory_usage is
>> > not a method for imagick, other circumstances which occupy huge memory
>> can
>> > use this method to
>> > ensure the system have enough free memory.
>>
>> OK,
>>
>> one thing I didn't understand is "why should you want check de zend
>> memory usage when there is a memory_limit parameter in PHP.ini " ?
>> does'nt it do the same at PHP layer when allocating ?
>>
>>
> Obviously you didn't read the original mail, and the links inside:
>
>
> http://groups.google.com/group/highload-php-en/browse_thread/thread/1882a=
3b2257dcc5c/ea73892cea011541?lnk=3Dgst&q=3Dgaochunhui#ea73892cea011541
>
> The problem here is that PHP wouldn't free any allocated memory untill
> the process exits, so there's the risk of memory exhaustion if too
> many PHP processes were running, even though each process wouldn't
> exceed PHP's memory_limit.
>
> My suggestion is more about releasing the allocated memory as soon as
> possible. That is, this option is similar to "max_requests".
> PHP-FPM would kill the PHP process if the requests a process handled
> exceed max_requests, and similarly, PHP-FPM should kill the PHP
> process whose memory usage exceeds "exit_on_memory_exceeds".
>
> So one of your lib (for example imagick) leaks memory, on the long run, i=
t
> will exhaust the memory limit, and will kill a totaly request.
> You can set that how many request should be served with one worker, but y=
ou
> can't soft limit it's memory consumption.
> This is what the patch does:
> if you set the hard limit: (memory_limit) you can guarante that no proces=
s
> will use more memory, because if it tries, it will fail.
> and you can set soft limit, if that reached, the process will die and
> respawn after finishing the current request.
>
> Tyrael
>

Btw: did you know about
http://php.net/manual/en/function.apache-child-terminate.php I just noticed
a few days ago, obviously, you can't use with cgi/fastcgi/php-fpm but for
apache, it does exactly what you need, except that you have to execute from
userland.
So I think it would be a good idea, to generally implement a soft/hard limi=
t
for memory allocation: if soft fails, the process terminates after the
request, if the hard limit fails, it is terminated instantly.

Tyrael

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