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Date: Wed, 13 Apr 2016 23:55:49 +0800
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Subject: Proposal: Startup snapshot for optimizing app load time
From: cornelius.howl@gmail.com (Lin Yo-An)

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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)

However, if we can support a simple syntax to describe what is doing
"bootstrap", we are able to create a startup snapshot from it.


The proposal here want to introduce some new syntax to optimize app load
time though the below syntax:

    bootstrap "vendor/autoload.php";  // caches the context after running
this script.

Or

    bootstrap {
           require "vendor/autoload.php";
           // do something else for making app ready
    };

And of course, we might detect the bootstrap script automatically without
creating new syntax and opcodes, but I think it's hard to do because PHP
applications can be written by many ways...


Questions
========

I don't know if this approach is doable or not. Or maybe we can support
this in a separated extension instead of changing the zend core?

Do you guys think it's doable? would you like to share your idea for this?






Best Regards,

Yo-An Lin

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