Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:92426
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: unknown (pb1.pair.com: domain php.net does not designate 212.27.42.2 as permitted sender)
To: Lin Yo-An <cornelius.howl@gmail.com>,
 "internals@lists.php.net" <internals@lists.php.net>
References: <CAKSD0w6ji0JgnnU0BSCv64_bu+RNnLTRyz7XPyCv2gcK-+6BBg@mail.gmail.com>
Message-ID: <5715312D.4050904@php.net>
Date: Mon, 18 Apr 2016 21:10:37 +0200
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101
 Thunderbird/38.7.2
MIME-Version: 1.0
In-Reply-To: <CAKSD0w6ji0JgnnU0BSCv64_bu+RNnLTRyz7XPyCv2gcK-+6BBg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Subject: Re: [PHP-DEV] Proposal: Startup snapshot for optimizing app load time
From: francois@php.net (=?UTF-8?Q?Fran=c3=a7ois_Laupretre?=)

Hi,

Le 13/04/2016 17:55, Lin Yo-An a écrit :
> Hi internals,
>
>
> The javascript engine V8 uses a strategy called "startup snapshot" to
> optimize app load time (see
> http://v8project.blogspot.tw/2015/09/custom-startup-snapshots.html for more
> details)
>
> The approach used by V8 creates a snapshot from heap, so the V8Context
> could be reused directly without re-running the bootstraping code.
>
> I think running javascript app in the browser is somehow like we run php
> script for each requests where the app bootstrapping code is required to be
> executed repeatedly for each request.
>
> Currently, our opcache extension can cache the byte codes, but the byte
> codes still need to be executed every time when bootstrapping an app, and
> which increases the overhead for each request.
>
> For example, a lot of applications use composer to initialize the class
> loader via the statement below:
>
>      require "vendor/autoload.php";
>
> The statement above produces thousands of byte code to run, which is to
> make an app ready. (If you use vld extension to show the opcodes)
>

You are mixing 2 related mechanisms here : code persistence and data 
persistence.

Code persistence (reloading the same code again and again in each 
request) is achieved through the autoloader. Autoloading, compbined with 
opcache provides a very fast mechanism to retrieve class definitions. If 
you measure the time taken by your 'require "vendor/autoload.php"' 
stance, you should find it to be extremely fast (with opcache on, of 
course).

Data persistence is another question: the need here is to save and 
restore object instances. Several cache mechanisms exist for this, 
saving and restoring via serialize/unserialize. The problem with your 
'bootstrap' approach (apart from the fact that it is not physically 
possible in PHP) is that you won't want to snapshot the *whole* 
environment, because you always want to keep at least some dynamic 
context. What you actually want to 'snapshot' is a set of well-defined 
object instances. So, the question, IMO, is to develop a mechanism 
faster than the current ones to store and retrieve object instances from 
memory.

Regards

François