Don't use comments?

[spinitron]

Don't use comments?

[spinitron]

Yes, it saves opcache shared memory. The memory load for each PHP file is reduced by the number of bytes of comments in the file, iiuc. I agree that it's not necessary to implement without reflecting on comments but I think it's desirable.

We cannot in general quantify the benefit of setting opcache.save_comments=0 since it depends entirely on the project. But I can offer some general qualitative observations...

• Lots of comments is rather common these days. For example, the libs we depend on often document themselves entirely with comments. So it could be a significant fraction of total SHM demand.
• Your README offers performance as a selling point while it impacts the SHM load of all code in that opcache.
• I assume opcache offers the config option because it can yield real operational benefit.
• Portable, runtime-independent code is nice.
• Comment reflection is a bit, how should I put it diplomatically?, not what you might expect a modern software textbook to recommend as "good practice".

[spinitron]

@cebe, yes I'm sure it can. It can be solved also with conventional programming.

But the issue with opcache is actually small enough. Allocate enough memory to opcache and stop worrying about it.

In my case the problem has gotten smaller with time as I use fewer comments. With type hints and good names for functions and parameters, comments can be redundant.

[cebe]

does opcache.save_comments=0 really safe some resources or improve speed? In general composition of markdown features could be implemented in a different way, but I do not think it is really necessary.

[spinitron]

Fwiw, OPcache stats from my servers currently show

• number of scripts 1430
• 11 of them under cebe/markdown
• 36.3 MiB without comments
• 39.6 MiB with comments, about 9% more

Not a huge difference but it's not insignificant.

[spinitron]

Nothing much changed. Detailed opcache status below shows server A and B have almost identical opcache use (no surprise, they have almost identical load). The only important difference is used_memory which is ~10% more with with comments. (This opcache has been up for just over a month.)

stat	A	B
opcache_enabled	true	true
cache_full	false	false
restart_pending	false	false
restart_in_progress	false	false
memory_usage
used_memory	39580576	43352104
free_memory	77943056	73007632
wasted_memory	16694096	17857992
current_wasted_percentage	12.43807077407837	13.305240869522095
interned_strings_usage
buffer_size	8388608	8388608
used_memory	3365656	3353072
free_memory	5022952	5035536
number_of_strings	60879	60802
opcache_statistics
num_cached_scripts	1614	1613
num_cached_keys	2225	2226
max_cached_keys	16229	16229
hits	2904881093	3074112339
start_time	1535933633	1535720837
last_restart_time	0	0
oom_restarts	0	0
hash_restarts	0	0
manual_restarts	0	0
misses	99128	160821
blacklist_misses	53734850	60452796
blacklist_miss_ratio	1.8161549426196841	1.928487429157587
opcache_hit_rate	98.18049468407227	98.0663822659208

[cebe]

Thank you for the detailed stats!

[Ayesh]

I'm interested in to see if there is any development in this issue.

Ubuntu, Debian and oenrej/php PHP packages have default configuration opcache.save_comments=1, but I personally turn it off save some opcache space. This is my only blocker that prevents me using this awesome package.

Thank you.

[cebe]

If you want to use this lib without comments, you could extend the markdown flavor class you want to use and override the following method:

markdown/Parser.php

Lines 254 to 285 in eeb1bf6

	/**
	* Returns a map of inline markers to the corresponding parser methods.
	*
	* This array defines handler methods for inline markdown markers.
	* When a marker is found in the text, the handler method is called with the text
	* starting at the position of the marker.
	*
	* Note that markers starting with whitespace may slow down the parser,
	* you may want to use [[renderText]] to deal with them.
	*
	* You may override this method to define a set of markers and parsing methods.
	* The default implementation looks for protected methods starting with `parse` that
	* also have an `@marker` annotation in PHPDoc.
	*
	* @return array a map of markers to parser methods
	*/
	protected function inlineMarkers()
	{
	$markers = [];
	// detect "parse" functions
	$reflection = new \ReflectionClass($this);
	foreach($reflection->getMethods(ReflectionMethod::IS_PROTECTED) as $method) {
	$methodName = $method->getName();
	if (strncmp($methodName, 'parse', 5) === 0) {
	preg_match_all('/@marker ([^\s]+)/', $method->getDocComment(), $matches);
	foreach($matches[1] as $match) {
	$markers[$match] = $methodName;
	}
	}
	}
	return $markers;
	}

if you hardcode the array of markers and function names it should all work with opcache.save_comments=0.

I might add some docs about it and possibly also add a configuration option for it...

[cebe]

this can be solved in PHP 8 by using attributes: https://wiki.php.net/rfc/attributes_v2