Performance tricks

If you:

• use php-v8 extension for short-lived tasks or
• you have your Context short-lived

it is likely that you won’t be able benefit from V8 runtime optimizations. However, you can still improve your performance.

Important note: all caching techniques are V8 version-specific and platform specific, some caches won’t even work on different CPU with different instructions set, you have to test following techniques for your environment and infrastructure and be ready to fallback to raw, cache-less flow.

Let’s say you have an typical Hello, world! script:

<?php declare(strict_types=1);

use V8\{
    Isolate,
    Context,
    StringValue,
    Script,
};

$script_source_string = "function say() { return 'Hello' + ', World!'}; say()";

$isolate = new Isolate();
$context = new Context($isolate);
$source  = new StringValue($isolate, $script_source_string);

$script = new Script($context, $source);
$result = $script->run($context);

echo $result->value(), PHP_EOL;

Let’s reshape it a bit to make it more suitable for further tweaks by introducing ScriptCompiler:

<?php declare(strict_types=1);

use V8\{
    Isolate,
    Context,
    StringValue,
    ScriptCompiler,
};

$script_source_string = "function say() { return 'Hello' + ', World!'}; say()";

$isolate       = new Isolate();
$context       = new Context($isolate);
$source_string = new StringValue($isolate, $script_source_string);
$source        = new ScriptCompiler\Source($source_string);
$script        = ScriptCompiler::compile($context, $source);

$result = $script->run($context);

echo $result->value(), PHP_EOL;

Script code cache

Using script code cache could boost your performance from 5% to 25% or even more, itlargely depends on your script and host. On slower machines it may give you better result in terms of performance gain %%, while on faster it may be not so large, according to performance benchmark.

<?php declare(strict_types=1);

use V8\{
    Isolate,
    Context,
    StringValue,
    ScriptCompiler,
};

$script_source_string = "function say() { return 'Hello' + ', World!'}; say()";

$isolate       = new Isolate();
$context       = new Context($isolate);
$source_string = new StringValue($isolate, $script_source_string);
$source        = new ScriptCompiler\Source($source_string);

// Generating script cache. Normally you want to cache this data somewhere else
// either on filesystem, in database or in memory. Redis could be your friend
// but don't let it be your memory hog.
$unbound_script = ScriptCompiler::compileUnboundScript($context, $source);
$cached_data = ScriptCompiler::createCodeCache($unbound_script, $source_string);

// Here we utilize script cache
$source = new ScriptCompiler\Source($source_string, null, $cached_data);
$script = ScriptCompiler::compile($context, $source, ScriptCompiler::OPTION_CONSUME_CODE_CACHE);

if ($cached_data->isRejected()) {
    throw new RuntimeException('Script code cache rejected!');
}

$result = $script->run($context);

echo $result->value(), PHP_EOL;

Isolate startup data

Startup data can speedup your context creation by populating them with script run result. It can save from 1% to 3%, so it’s not so effective as script code cache, however, the benchmark was done on using quite simple example, so if you have a lot of entities that you need to bootstrap your context with, your saving may be more.

<?php declare(strict_types=1);

use V8\{
    Isolate,
    Context,
    StringValue,
    ScriptCompiler,
    StartupData,
};

$script_source_string = "function say() { return 'Hello' + ', World!'}; say()";

// Same here, you are likely want to store it in some quick and cheap to access storage
$startup_data = StartupData::createFromSource($script_source_string);

$isolate       = new Isolate($startup_data);
$context       = new Context($isolate);
$source_string = new StringValue($isolate, $script_source_string);
$source        = new ScriptCompiler\Source($source_string);

$script = ScriptCompiler::compile($context, $source);

$result = $script->run($context);

echo $result->value(), PHP_EOL;

Combining both approaches

Combining both techniques is you friend in boosting performance:

<?php declare(strict_types=1);

use V8\{
    Isolate,
    Context,
    StringValue,
    ScriptCompiler,
    StartupData,
};

$script_source_string = "function say() { return 'Hello' + ', World!'}; say()";

$startup_data = StartupData::createFromSource($script_source_string);

$isolate       = new Isolate($startup_data);
$context       = new Context($isolate);
$source_string = new StringValue($isolate, $script_source_string);
$source        = new ScriptCompiler\Source($source_string);

$unbound_script = ScriptCompiler::compileUnboundScript($context, $source);
$cached_data = ScriptCompiler::createCodeCache($unbound_script, $source_string);

$source = new ScriptCompiler\Source($source_string, null, $cached_data);
$script = ScriptCompiler::compile($context, $source, ScriptCompiler::OPTION_CONSUME_CODE_CACHE);

if ($cached_data->isRejected()) {
    throw new RuntimeException('Script code cache rejected!');
}

$script = ScriptCompiler::compile($context, $source);

$result = $script->run($context);

echo $result->value(), PHP_EOL;

Benchmarks

Note, that your mileage may varies so you are highly encouraged to run benchmarks located under project’s root /pref folder by yourself on your hardware, in your infra and even with your js script.

From Ubuntu in Docker on macOS

4 cores, 16Gb memory

# php -v
PHP 7.2.2-3+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Feb  6 2018 16:11:23) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.2-3+ubuntu16.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

# php --ri v8
V8 support => enabled
Version => v0.2.1-master-dev
Revision => 5d7c3e4
Compiled => Feb 25 2018 @ 11:29:00

V8 Engine Compiled Version => 6.6.313
V8 Engine Linked Version => 6.6.313

Less is better

subject	mode	stdev	rstdev	diff (less is better)
Cold Isolate, no code cache	3,602.599us	49.778us	1.38%	+26.98%
Cold Isolate, with code cache	2,885.638us	39.775us	1.36%	+2.86%
Warm Isolate, no code cache	3,489.959us	44.036us	1.27%	+22.46%
Warm Isolate, with code cache	2,813.156us	43.351us	1.53%	0.00%

From macOS host

4 cores, 16Gb memory

$ php -v
PHP 7.2.2 (cli) (built: Feb  1 2018 11:50:40) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
    with Zend OPcache v7.2.2, Copyright (c) 1999-2018, by Zend Technologies

$ php --ri v8
V8 support => enabled
Version => v0.2.1-master-dev
Revision => 5d7c3e4
Compiled => Feb 25 2018 @ 11:42:00

V8 Engine Compiled Version => 6.6.313
V8 Engine Linked Version => 6.6.313

subject	mode	stdev	rstdev	diff (less is better)
Cold Isolate, no code cache	8,732.585us	97.889us	1.11%	+6.90%
Cold Isolate, with code cache	8,290.880us	141.583us	1.69%	+1.78%
Warm Isolate, no code cache	8,722.684us	104.547us	1.19%	+6.68%
Warm Isolate, with code cache	8,194.924us	70.345us	0.85%	0.00%