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Date: Thu, 1 Apr 2010 18:03:11 +0200
Reply-To: speedy <speedy.spam@gmail.com>
Message-ID: <19610230188.20100401180311@gmail.com>
To: Rasmus Lerdorf <rasmus@lerdorf.com>
CC: PHP Developers Mailing List <internals@lists.php.net>
In-Reply-To: <4BB4BA13.2070706@lerdorf.com>
References: <1941231697.20100401163215@gmail.com> <4BB4BA13.2070706@lerdorf.com>
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Subject: Re: [PHP-DEV] php and multithreading (additional arguments)
From: speedy.spam@gmail.com (speedy)

Hello Rasmus,

Thursday, April 1, 2010, 5:21:55 PM, you wrote:

> On 04/01/2010 07:32 AM, speedy wrote:
>>       1. Imagine that from time to time, some background processing take=
s 1
>>       second of CPU time - w/o multithreading, all your async operations,
>>       like accepting a connection to a socket, aio or others are basical=
ly
>>       stalled. So, async is a good approach, but does not work as a magic
>>       wand for all problem spaces. Alternatively, you could fork and the=
n do the
>>       processing, but then the state syncing of the forked background pr=
ocessing
>>       results with the main thread requires a whole new protocol / switc=
hing to
>>       interprocess communication, which makes such developments unnecess=
arily
>>       hard. Threads exist for a _reason_ not only because they sound coo=
l.

> There are plenty of mechanisms/protocols for doing this.  Gearman works
> extremely well for managing out-of-band jobs like this, for example.

Yes, but sometimes, esp. in more real-time oriented applications, state mer=
ging is
very hard to do - though I agree that protocols and mechanisms exist for ou=
t of
band processing, there are plenty of cases in which they are suboptimal.

>>       2. Without thread support, it is not possible to use multi-core pr=
ocessing
>>       paradigms directly from PHP - which means PHP relies on external f=
rameworks for
>>       that feature, which, in a sense, makes it a non-general-purpose la=
nguage.
>>       It _could become_ a general purpouse tool, if it had proper multi-=
threading
>>       support built-in.

> PHP is not a general-purpose language and there are no plans to make it
> one.  Your OS provides scheduling and is responsible for making best use
> of your multiple cores.  With many concurrent web requests your multiple
> cores should be put to good use.

Current situational facts are against that claim - with PHP delivered as a =
CLI
interpreter, and via that route, having more and more software applications=
 written
outside the web serving scope/domain, PHP has spontaneously made strides in=
to
becoming a general purpouse tool.

I think the only remaining step in that direction is to have the native
multi-threading support. I plan to check out how hard would that be, and se=
e how
many people would be needed for developing that feature in some reasonable =
time-frame.

Also, keep in mind that the web is slowly shifting towards real-time commun=
ication
/ streaming with emergence of Comet, HTML5 Web Sockets etc. There are alrea=
dy many web
server implementations specialising in that, and PHP is _not_ their languag=
e of choice.

> -Rasmus

--=20
Best regards,
 speedy                            mailto:speedy.spam@gmail.com