Re: [PHPLIB] Re: [PHP3] persistent data From: Kristian Koehntopp (kris <email protected>)
Date: 03/30/00

On Thu, Mar 30, 2000 at 02:33:28PM +0200, Sascha Schumann wrote:
> Well, the penalty for storing simple strings is still quite high.

Yes, that is true. That is why the session module in PHP4 is
worthwile the effort.

Still PHPLIB with a MySQL backend was fast enough to keep
Zend.COM online through their /. 15 minutes of fame. I think we
can consider that performant enough for most PHPLIB users.

> Shared memory reduces the number of system calls even further, and
> thus should be faster for keeping this kind of data around. Less
> context switches, more speed.

In PHP4 shared memory sessions the system overhead to sessions
became so small that the limiting factor is the locking nature
of sessions themselves: If process #1 is producing a page for
session #17, it has to keep a lock on _all_ session variables
pertaining to session #17. Process #2, belonging to the same
session (for example in a frameset), is being locked out and
effectively all pages of that session are serialized.

That were not the case if PHP4 sessions were able to lock
individual variable names or even individual values (I would not
pursue the latter, it is a very difficult project). Of course
such a thing is impossible to do efficiently with PHPLIB
sessions... And of course such behaviour should be optional as
it requires support from the code using it (i.e. you have to
wrap locking/unlocking instructions around your variable usage).

The best you can to in PHPLIB is not to use locking at all (the
default) and to leave of the page_close() at all but one page of
a frameset (making the noncontent pages of the frameset
read-only with respect to the session data).

Kristian

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