Benchmark: WordPress load speed on php.wasm and Kandelo

[mho22]

How fast WordPress loads in the browser on three runtimes. Each new run gets its own comment.

• classic: Playground on php.wasm.
• posix-kernel: Playground on the Kandelo kernel, with ?experimental=kandelo ([wasm-posix-kernel] WordPress Playground Web Kandelo Beta - Proof of concept #3957).
• kandelo: Kandelo's own browser app, profile wordpress-sqlite.

Results

Run of 2026-10-19. Median of 5 rounds, min–max in parentheses. Lower is better.

Metric	classic	posix-kernel	kandelo
Cold load	1.49 s (1.48–1.60)	7.53 s (7.44–7.62)	16.36 s (16.33–16.45)
Warm load	1.60 s (1.50–1.60)	6.95 s (6.84–7.05)	16.20 s (16.09–16.30)
Hot load	162 ms (94–166)	572 ms (567–578)	416 ms (403–444)
Bytes downloaded	34.9 MiB	47.7 MiB	110.0 MiB
Memory	1214 MiB (1210–1230)	3460 MiB (3399–3491)	3500 MiB (3461–3510)
wp-admin load	393 ms (392–403)	979 ms (958–982)	818 ms (797–826)
REST request	39 ms (38–40)	485 ms (477–486)	283 ms (269–311)

Metrics

Each round starts a new Chromium with an empty cache and empty storage.

• Cold load: from page.goto() until the WordPress front page renders.
• Warm load: from page.reload() until the front page renders again, with a full HTTP cache.
• Hot load: median of 5 front-page loads inside the running site.
• Bytes downloaded: bytes sent by the server during the cold load.
• Memory: resident memory of Chromium and all its child processes, after the cold load.
• wp-admin load: open wp-admin/ until the admin bar renders, logged in.
• REST request: median of 5 fetch() calls to ?rest_route=/wp/v2/posts.

Setup

Production builds served from localhost, with the deployment headers of each target. Apple M4 Max, Chromium.

Playground: af405ba21
Kandelo submodule: 3c9c514ba
Kandelo dist: Automattic/kandelo main 90283c479
Playground WordPress / PHP: 7.0 / 8.3

[mho22]

posix-kernel with #4469

#4469 boots from the installed database, probes the server with /wp-includes/version.php, and runs php-fpm with the opcache file cache.

Median of 5 rounds, min–max in parentheses.

Metric	#3957	#4469	Change
Cold load	7.53 s (7.44–7.62)	5.63 s (5.44–10.54)	−25 %
Warm load	6.95 s (6.84–7.05)	5.18 s (5.09–5.23)	−25 %
Hot load	572 ms (567–578)	339 ms (337–408)	−41 %
Bytes downloaded	47.7 MiB	48.4 MiB	+0.7 MiB
Memory	3460 MiB (3399–3491)	3500 MiB (3458–3541)	+1 %
wp-admin load	979 ms (958–982)	791 ms (782–897)	−19 %
REST request	485 ms (477–486)	252 ms (251–310)	−48 %

Metric	classic	posix-kernel	kandelo
Cold load	1.68 s (1.55–1.75)	5.63 s (5.44–10.54)	16.63 s (16.50–16.64)
Warm load	1.59 s (1.50–1.59)	5.18 s (5.09–5.23)	16.35 s (16.23–16.46)
Hot load	163 ms (115–164)	339 ms (337–408)	369 ms (345–401)
Bytes downloaded	35.4 MiB	48.4 MiB	110.0 MiB
Memory	1219 MiB (1217–1232)	3500 MiB (3458–3541)	3489 MiB (3449–3527)
wp-admin load	399 ms (396–407)	791 ms (782–897)	807 ms (787–831)
REST request	39 ms (39–62)	252 ms (251–310)	275 ms (256–287)

[mho22]

posix-kernel with Automattic/kandelo#1545

• File cache only: opcache with opcache.file_cache_only=1, as in [wasm-posix-kernel] WordPress Playground Web Kandelo Performance - Proof of concept #4469. Each request loads every compiled script from a file.
• Shared memory: Packages: Map the PHP opcache shared memory MAP_PRIVATE Automattic/kandelo#1545 maps the opcache shared memory MAP_PRIVATE, so each php-fpm worker keeps its compiled scripts in memory. Flags: opcache.file_cache_only=0, opcache.memory_consumption=64.

Medians of 2 alternating passes of 3 rounds (pass 1 / pass 2):

Metric	#4469, file cache only	Automattic/kandelo#1545, shared memory	classic
Cold load	6.23 / 6.09 s	5.37 / 5.79 s	1.60 / 1.80 s
Warm load	5.82 / 5.66 s	4.87 / 5.45 s	1.62 / 1.62 s
Hot load	426 / 409 ms	164 / 185 ms	174 / 175 ms
wp-admin load	983 / 940 ms	620 / 620 ms	427 / 433 ms
REST request	336 / 325 ms	65 / 67 ms	42 / 42 ms
Bytes downloaded	48.4 MiB	48.6 MiB	35.6 MiB
Memory	3472 / 3481 MiB	3611 / 2459 MiB	1221 / 1227 MiB

[mho22]

posix-kernel with Automattic/kandelo#1545 on PHP 8.5.12

Kandelo main now ships PHP 8.5.12 with opcache built in, so Automattic/kandelo#1545 was rebased on it. This run replaces the previous comment, which measured PHP 8.3.15.

• File cache only: opcache with opcache.file_cache_only=1, as in [wasm-posix-kernel] WordPress Playground Web Kandelo Performance - Proof of concept #4469. Each request loads every compiled script from a file.
• Shared memory: Packages: Map the PHP opcache shared memory MAP_PRIVATE Automattic/kandelo#1545 maps the opcache shared memory MAP_PRIVATE, so each php-fpm worker keeps its compiled scripts in memory. Flags: opcache.file_cache_only=0, opcache.memory_consumption=64.

Median of 5 rounds, min–max in parentheses.

Metric	#4469, file cache only	Automattic/kandelo#1545, shared memory	classic
Cold load	5.43 s (5.41–5.53)	5.27 s (5.22–5.41)	1.49 s (1.47–1.58)
Warm load	5.14 s (4.95–5.34)	4.83 s (4.83–5.03)	1.60 s (1.49–1.70)
Hot load	422 ms (418–429)	166 ms (155–176)	157 ms (95–164)
wp-admin load	892 ms (888–914)	583 ms (562–600)	391 ms (385–398)
REST request	317 ms (316–327)	71 ms (64–75)	38 ms (38–39)
Bytes downloaded	50.9 MiB	51.1 MiB	35.6 MiB
Memory	3711 MiB (3676–3726)	3843 MiB (3814–3869)	1221 MiB (1215–1222)

Syscalls for one warm REST request, from the Playground CLI on Node with WASM_POSIX_PROFILE=1, median of 7 back-to-back requests:

• File cache only: 6,011. Each request opens, reads and closes about 1,060 cache files.
• Shared memory: about 600. About 1,460 when opcache checks the timestamps of the scripts, once every 2 s in each worker (opcache.revalidate_freq=2).

Playground: abff3544f (#4469)
Kandelo submodule: 67cbecdc2 (Automattic/kandelo#1545, PHP 8.5.12)
WordPress: 7.0
PHP: 8.3 (classic), 8.5.12 (posix-kernel)

[mho22]

posix-kernel with MariaDB

This run replaces SQLite with MariaDB in posix-kernel and compares it with classic on SQLite. classic cannot run MariaDB: php.wasm has no processes and no sockets.

• classic: php.wasm with the SQLite integration plugin, unchanged.
• posix-kernel with MariaDB: [wasm-posix-kernel] WordPress Playground Web Kandelo Performance - Proof of concept #4469 with Packages: Map the PHP opcache shared memory MAP_PRIVATE Automattic/kandelo#1545 on PHP 8.5.12, the shared memory setup of the previous comment. The SQLite plugin, its db.php drop-in and the shipped SQLite database are deleted. mariadbd starts before php-fpm, with the flags of Kandelo's wordpress-mariadb service. WordPress connects through /tmp/mysql.sock.

Median of 5 rounds, min–max in parentheses.

Metric	classic, SQLite	posix-kernel, MariaDB	Ratio
Cold load	1.49 s (1.48–1.59)	5.43 s (5.32–5.56)	3.6×
Warm load	1.50 s (1.50–1.59)	5.05 s (4.94–5.15)	3.4×
Hot load	158 ms (155–161)	150 ms (147–159)	0.95×
wp-admin load	395 ms (389–401)	575 ms (552–585)	1.5×
REST request	39 ms (38–40)	59 ms (57–67)	1.5×
Bytes downloaded	35.9 MiB	55.1 MiB	+19.2 MiB
Memory	1226 MiB (1224–1236)	4441 MiB (3885–4465)	3.6×

Against posix-kernel with SQLite from the previous comment, measured on another day:

Metric	posix-kernel, SQLite	posix-kernel, MariaDB
Cold load	5.27 s	5.43 s
Warm load	4.83 s	5.05 s
Hot load	166 ms	150 ms
wp-admin load	583 ms	575 ms
REST request	71 ms	59 ms
Bytes downloaded	51.1 MiB	55.1 MiB
Memory	3843 MiB	4441 MiB

MariaDB adds about 0.2 s to the boot, 4 MiB to the download and 600 MiB of memory. It makes REST requests about 12 ms faster and front page loads about 16 ms faster. The kernel, not the database, causes most of the gap to classic.

Setup:

• Database: /data is copied from the wordpress-mariadb image built by Kandelo main, with WordPress 7.0 already installed. It ships as a 113 KB gzip file. The site title is "WordPress on Kandelo". Both targets log in as admin / password.
• Persistent connections: class-wpdb.php gets the same patch as in Kandelo's LAMP image, so each php-fpm worker reuses its mysqli connection.
• Kernel workers: the limit goes from 8 to 24, as in Kandelo's wordpress-mariadb profile. mariadbd needs the extra threads.
• Readiness: the boot waits until a mysqli connection succeeds, not only until nginx answers.
• MariaDB binary: no published build matches the ABI of the Kandelo submodule, so mariadbd.wasm is built from it with xtask bootstrap mariadb.

Memory of posix-kernel grows between rounds: 3885 MiB in round 1, about 4450 MiB in rounds 2 to 5. Memory of classic stays flat. The cause is not known yet.

Playground: abff3544f (#4469)
Kandelo submodule: 67cbecdc2 (Automattic/kandelo#1545, PHP 8.5.12)
MariaDB: 10.5.28
WordPress: 7.0
PHP: 8.3 (classic), 8.5.12 (posix-kernel)