Improve performance in the WP_Theme_JSON class by simplifying calls to array functions #3555

aristath · 2022-11-03T06:26:23Z

Trac ticket: https://core.trac.wordpress.org/ticket/56974

This PR simplifies expensive array-functions calls where appropriate.

Attaching some profiling results to showcase the impact.

Before (trunk):

After (with this PR):

All numbers in the screenshots above use milliseconds, and the impact of these seemingly simple changes is bigger than expected, shaving off more than 200ms. Of course those numbers are a bit inflated due to the fact that profiling slows down a page significantly, but the overall improvement on the page-load is more than 3%.

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

props @jrfnl 🙌

src/wp-includes/class-wp-theme-json.php

These 2 functions only differ if the value in one of the items of the array has a value of null - something that can't ever happen in this scenario. isset() is significantly faster so changing it makes sense in this context.

Checked each of these cases to ensure that value is never null

spacedmonkey · 2022-11-08T17:56:36Z

While doing some profiling, I noticed there are still calls to _wp_array_get. This calls array_key_exists, which is expensive. I wonder if we could avoid these somehow.

spacedmonkey · 2022-11-08T18:03:50Z

src/wp-includes/class-wp-theme-json.php

@@ -2317,6 +2343,9 @@ public function merge( $incoming ) {
 					) {
 						_wp_array_set( $this->theme_json, $path, $content );
 					} else {
+						$slugs_node = static::get_default_slugs( $this->theme_json, $node['path'] );
+						$slugs      = array_merge_recursive( $slugs_global, $slugs_node );


Why is this needed?

It wasn't added, it was just moved here. 😉
A few lines above we were calling these 2 on the previous foreach loop (used to be line 2281), so they were always running. Instead of always calling them, we moved them here where they are actually used. This way these rather expensive calls run fewer times, only when necessary.

jrfnl · 2022-11-08T23:57:52Z

While doing some profiling, I noticed there are still calls to _wp_array_get. This calls array_key_exists, which is expensive. I wonder if we could avoid these somehow.

I wouldn't worry too much about (or overestimate) the impact of array_key_exists().

array_key_exists() is not one of the typically expensive array_*() function calls.
Yes, isset() is generally speaking faster...
... BUT array_key_exists() has been opcode optimized in PHP since PHP 7.4 and what with the fast majority of WP users being on PHP 7.4 (or above), the performance difference will be negligible for most users.

Note: isset() and array_key_exists() also have a functional difference in how they treat a null value, so for array_key_exists() to be equivalent to isset(), it MUST be accompanied by a && $var !== null.

aristath · 2022-11-09T07:07:17Z

Note: isset() and array_key_exists() also have a functional difference in how they treat a null value, so for array_key_exists() to be equivalent to isset(), it MUST be accompanied by a && $var !== null.

Yeah, that's an important distinction!
In the comments I added for future reference to replace array_key_exists() with isset() (// Note: array_key_exists() should be replaced with an isset() check once WordPress drops support for PHP 5.6.), I checked the values in each case and only added that comment in cases where the value can not be null.
In one case the value can be null, and I added a comment in that one that // We need to use array_key_exists() instead of isset() because the value can be null. 👍

spacedmonkey · 2022-11-09T22:11:58Z

In trunk.

In this brunch.

felixarntz · 2022-11-10T00:01:02Z

@jrfnl @aristath Following up on array_key_exists: Makes sense not to overthink this in terms of performance impact compared to isset, however I had one follow up thought I wanted to at least raise here:

Most of the usage of array_key_exists here could be replaced with isset as the additional null consideration is irrelevant for most (if not all) of the code where it's used here.
Given that, there would be the alternative option of assigning the result to a variable and then calling isset on that variable.

For example, instead of:

if ( array_key_exists( $element, static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES ) ) {
}

Do:

$element_class_names = static::__EXPERIMENTAL_ELEMENT_CLASS_NAMES;
if ( isset( $element_class_names[ $element ] ) {
}

Again, not saying this is necessarily worth doing (and certainly not a blocker), but I'd be curious if the first or the last is generally faster. :)

felixarntz

The code changes here look solid to me!

I of course trust the benchmarking data provided in https://core.trac.wordpress.org/ticket/56974#comment:1, but it may additionally be helpful to quantify the performance gain here in milliseconds as well.

Given that parsing theme.json affects the wp_head action quite a bit (see also #3536), I thought I'd do a performance comparison there first. Based on 9 test runs, the median impact there is small but consistent:

With Twenty Twenty-Three (i.e. block theme): 26.63ms vs 27.78ms (~4% faster)
With Twenty Twenty-One (i.e. classic theme): 15.30ms vs 16.05ms (~5% faster)

See this spreadsheet for the full data.

So also in that regard it looks like a small but worthwhile win. Potentially I can do the same for more concretely the parsing of theme.json itself as that would be even closer to the changes here and allow us to quantify impact in that way too.

jrfnl · 2022-11-10T08:35:27Z

There's bound to be more room for improvement, but yes, let's take this step by step and I do believe this is a valuable step in that.

Re: assign+isset vs array_key_exists: as most array_key_exists() are only in place for PHP 5.6, might be more effective to re-open the discussion on dropping support for PHP 5.6 ... 😇

On that note - PHP 8.3 will bring another very useful improvement json_validate() (validate a JSON input before decoding without running the risk of the JSON tying up all the memory), but that is no doubt still a bridge too far ;-)

desrosj

Added a few nits.

src/wp-includes/class-wp-theme-json.php

…cket/57067.

desrosj

Looks good overall. Commented with a few small questions/suggestions, but none of them are really to be considered blockers.

src/wp-includes/class-wp-theme-json.php

felixarntz · 2022-11-11T01:49:41Z

Committed in https://core.trac.wordpress.org/changeset/54804.

oandregal · 2022-12-15T12:57:33Z

src/wp-includes/class-wp-theme-json.php

@@ -2035,7 +2056,9 @@ public function get_styles_for_block( $block_metadata ) {
 					// the feature selector. This may occur when multiple block
 					// support features use the same custom selector.
 					if ( isset( $feature_declarations[ $feature_selector ] ) ) {
-						$feature_declarations[ $feature_selector ] = array_merge( $feature_declarations[ $feature_selector ], $new_feature_declarations );
+						foreach ( $new_feature_declarations as $new_feature_declaration ) {
+							$feature_declarations[ $feature_selector ][] = $feature_declaration;


@aristath @desrosj @felixarntz @spacedmonkey @jrfnl @hellofromtonya

Shouldn't the variable assigned be $new_feature_declaration instead of $feature_declaration? This has been reported as problematic by the Gutenberg lint jobs (see conversation).

I haven't looked at what regression this introduced but it'd be good to create a follow-up PR fixing it and adding a test case.

@oandregal I concur. This is a bug which should be fixed.

Suggested change

$feature_declarations[ $feature_selector ][] = $feature_declaration;

$feature_declarations[ $feature_selector ][] = $new_feature_declaration;

🤦 yeah, looks like this was a typo.. Good catch 👍

Happens to the best of us ;-)

I'm not familiar with this code path, so asked folks to provide details for testing at WordPress/gutenberg#46579 (comment) so we can add a new unit test and gauge how severe this is.

AFAICS, this should go in the next 6.1 patch release.

Edit to clarify: I'm basing this assessment on the following:

It's very clearly a bug with an obvious fix.

It's likely a regression compared to previous behaviour.

aristath force-pushed the feature/pp-ari-wp-theme-json branch 2 times, most recently from 3ddcf7e to d0bc5f2 Compare November 3, 2022 08:40

aristath marked this pull request as ready for review November 3, 2022 09:05

jrfnl reviewed Nov 3, 2022

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src/wp-includes/class-wp-theme-json.php Outdated Show resolved Hide resolved

spacedmonkey requested review from spacedmonkey, felixarntz and hellofromtonya and removed request for felixarntz November 3, 2022 11:02

jrfnl mentioned this pull request Nov 3, 2022

PHP < 7.0: cannot use isset() on the result of an expression PHPCompatibility/PHPCompatibility#1301

Open

jrfnl and others added 19 commits November 8, 2022 09:19

WIP

9ca0b27

WIP step 2

57f0dba

WIP - step 3

58b0ff1

WIP Step 3b

d3bbd20

WIP - setp 4

c17341b

WIP - simplify it a little more

aa13245

WIP - step 5

188ce0f

WIP - side step 6

194368e

WIP - side step 7

8fed0c1

CS & cleanup

5fa9aae

replace array_key_exists with isset

979bfef

These 2 functions only differ if the value in one of the items of the array has a value of null - something that can't ever happen in this scenario. isset() is significantly faster so changing it makes sense in this context.

replace an array_merge with a foreach loop

be50567

Add an inline comment to avoid future refactors

6aa5ede

We can use isset() instead of array_key_exists() here (no null values)

4434b1d

replace array_merge with a foreach loop

505a4f8

replace array_merge with foreach loop in the flatten_tree method

0345837

replace array_key_exists() with isset()

8df441c

Checked each of these cases to ensure that value is never null

Replace more array_merge with foreach loops where appropriate

8c04874

Fix PHP 5.6 errors + added notes for the future

213e94b

aristath force-pushed the feature/pp-ari-wp-theme-json branch from 52ae187 to 213e94b Compare November 8, 2022 07:19

spacedmonkey requested a review from felixarntz November 8, 2022 17:55

spacedmonkey reviewed Nov 8, 2022

View reviewed changes

Merge branch 'trunk' into feature/pp-ari-wp-theme-json

8923cd8

felixarntz approved these changes Nov 10, 2022

View reviewed changes

desrosj requested changes Nov 10, 2022

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felixarntz added 2 commits November 10, 2022 14:08

Add comment references pointing to https://core.trac.wordpress.org/ti…

5730ac1

…cket/57067.

Merge branch 'trunk' into feature/pp-ari-wp-theme-json

4af0999

felixarntz requested a review from desrosj November 10, 2022 22:09

Merge branch 'trunk' into feature/pp-ari-wp-theme-json

abf51b6

felixarntz mentioned this pull request Nov 10, 2022

Backport: Gutenberg 43660 - Separator color bugfix #3522

Closed

desrosj approved these changes Nov 11, 2022

View reviewed changes

felixarntz added 2 commits November 10, 2022 17:30

Merge branch 'trunk' into feature/pp-ari-wp-theme-json

4889396

Clarify variable name.

7ecd0a8

felixarntz closed this Nov 11, 2022

jrfnl deleted the feature/pp-ari-wp-theme-json branch November 11, 2022 04:12

felixarntz mentioned this pull request Nov 22, 2022

Update which origins are queried for gutenberg_get_global_settings WordPress/gutenberg#45971

Merged

spacedmonkey mentioned this pull request Nov 25, 2022

Add WP_Object_Cache to the gutenberg_get_global_settings method WordPress/gutenberg#45372

Merged

oandregal reviewed Dec 15, 2022

View reviewed changes

oandregal mentioned this pull request Dec 15, 2022

Try: bundle WP_Theme_JSON class instead of inheriting per WordPress version WordPress/gutenberg#46579

Merged

aristath mentioned this pull request Jul 19, 2023

Fix block registration from metadata #3501

Closed

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Improve performance in the WP_Theme_JSON class by simplifying calls to array functions #3555

Improve performance in the WP_Theme_JSON class by simplifying calls to array functions #3555

aristath commented Nov 3, 2022 •

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	$feature_declarations[ $feature_selector ][] = $feature_declaration;
	$feature_declarations[ $feature_selector ][] = $new_feature_declaration;

Improve performance in the WP_Theme_JSON class by simplifying calls to array functions #3555

Improve performance in the WP_Theme_JSON class by simplifying calls to array functions #3555

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