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Date: Thu, 1 Apr 2010 22:16:41 -0700
Message-ID: <698DE66518E7CA45812BD18E807866CE03FA7EFF@us-ex1.zend.net>
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Thread-Topic: [PHP-DEV] php and multithreading (additional arguments)
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References: <1941231697.20100401163215@gmail.com> <g2i469956791004011604v210ad50dx89b65cd0d731cea7@mail.gmail.com>
To: "Dennis Hotson" <dennis.hotson@gmail.com>,
	"speedy" <speedy.spam@gmail.com>
Cc: <internals@lists.php.net>
Subject: RE: [PHP-DEV] php and multithreading (additional arguments)
From: andi@zend.com ("Andi Gutmans")

Hi,

I think that if we were ever to implement threading we would be best off
to enable spawning worker threads that have their own context with no
shared data (and therefore no requirement for locking). We could then
have a message passing API between the threads.
Advantages:
- Real multi-threading.
- Simple straightforward approach which doesn't require a comp. sci.
degree to use correctly.
- Very stable implementation.

You can tell by this that:
a) I think GIL is not the way to go. It's more complex, not truly
multi-threaded, and implementation may never be 100%.
b) True multi-threading with data sharing in my opinion is a recipe for
disaster. Not only because of the implementation complexities but I
think it makes life very hard for the developer and requires a lot of
sophistication.

So if I'd implement something I'd definitely do true multi-threading
with message passing (we basically already have the infrastructure with
TSRM to support that). Do I think this is a high priority item? Not
really but I can understand that it could add value to some. I think for
some Web requests it could actually allow for some parallel processing
with a rendezvous which could help reduce latency (not overall server
throughput).  Then again, there'd be some overhead for having a
thread-safe build so I don't see this as something that would be enabled
by the masses - at least not initially.

Andi