OPcache User Cache Performance Report

Generated at 2026-07-01T16:01:18+00:00. Times are in microseconds; lower is faster.

CLI repeated read13/13 UserCache winsMedian APCu/UserCache: 24.54x

CLI store2/13 UserCache winsMedian APCu/UserCache: 0.34x

FPM one fetch/request13/13 UserCache winsMedian APCu/UserCache: 5.44x

FPM hot read11/11 UserCache winsMedian APCu/UserCache: 52.06x

Environment

PHP	`8.6.0-dev (cli)`
Thread Safety	`NTS`
Binary	`/workspaces/php-src/sapi/cli/php`
System	`Linux 498c42d87ff4 7.0.11-orbstack-00360-gc9bc4d96ac70 #1 SMP PREEMPT Thu Jun 4 16:40:25 UTC 2026 aarch64`
opcache.user_cache_shm_size	`128M`
Loaded benchmark extensions	`zend_opcache, apcu, deepclone`

CLI Repeated Read

Workload	UserCache	APCu	DeepClone	APCu/UserCache
`constant_array`	0.157 usmedian 0.157	2.119 usmedian 2.111	2.199 usmedian 2.181	13.54x
`route_table_read`	0.191 usmedian 0.191	211.221 usmedian 200.922	184.798 usmedian 182.008	1,104.64x
`large_array`	0.151 usmedian 0.151	90.238 usmedian 89.690	90.461 usmedian 89.639	597.96x
`large_string`	0.113 usmedian 0.112	5.331 usmedian 5.356	5.539 usmedian 5.567	47.36x
`large_object_graph`	0.177 usmedian 0.178	92.972 usmedian 91.569	100.508 usmedian 101.000	523.85x
`metadata_object_read`	0.250 usmedian 0.251	179.818 usmedian 179.112	178.231 usmedian 177.878	717.87x
`metadata_object_fetch_mutate`	0.325 usmedian 0.324	175.146 usmedian 174.267	179.524 usmedian 179.555	539.26x
`safe_direct_object`	0.542 usmedian 0.542	2.381 usmedian 2.370	4.044 usmedian 4.054	4.39x
`spl_collection_object`	0.794 usmedian 0.793	19.485 usmedian 19.384	20.772 usmedian 20.650	24.54x
`spl_linked_collection_object`	1.698 usmedian 1.748	19.370 usmedian 19.240	20.930 usmedian 20.855	11.41x
`spl_heap_object`	1.306 usmedian 1.302	31.244 usmedian 30.762	31.699 usmedian 31.615	23.93x
`carbon_datetime_object`	30.369 usmedian 29.744	180.527 usmedian 178.848	225.110 usmedian 224.546	5.94x
`carbon_model_object`	30.239 usmedian 30.093	192.792 usmedian 191.382	221.118 usmedian 220.696	6.38x

CLI Store

Workload	UserCache	APCu	DeepClone	APCu/UserCache
`constant_array`store trade-off note	3.136 usmedian 3.135	1.258 usmedian 1.255	1.319 usmedian 1.321	0.40x
`route_table_read`store trade-off note	322.105 usmedian 320.367	87.303 usmedian 86.353	103.537 usmedian 103.618	0.27x
`large_array`store trade-off note	167.485 usmedian 164.459	49.800 usmedian 49.703	64.191 usmedian 64.132	0.30x
`large_string`store trade-off note	11.083 usmedian 11.077	4.318 usmedian 4.315	12.919 usmedian 12.876	0.39x
`large_object_graph`store trade-off note	161.895 usmedian 161.823	51.788 usmedian 52.548	64.944 usmedian 64.766	0.32x
`metadata_object_read`store trade-off note	335.535 usmedian 334.894	92.052 usmedian 91.735	110.168 usmedian 109.922	0.27x
`metadata_object_fetch_mutate`store trade-off note	343.825 usmedian 344.967	90.337 usmedian 90.251	111.316 usmedian 111.411	0.26x
`safe_direct_object`store trade-off note	2.933 usmedian 2.919	1.212 usmedian 1.206	3.255 usmedian 3.250	0.41x
`spl_collection_object`store trade-off note	35.566 usmedian 35.379	11.036 usmedian 11.010	16.115 usmedian 16.133	0.31x
`spl_linked_collection_object`store trade-off note	31.725 usmedian 31.790	11.770 usmedian 11.742	16.003 usmedian 15.975	0.37x
`spl_heap_object`store trade-off note	55.895 usmedian 55.773	18.768 usmedian 18.656	24.118 usmedian 24.076	0.34x
`carbon_datetime_object`	203.404 usmedian 203.849	289.868 usmedian 289.499	360.186 usmedian 360.624	1.43x
`carbon_model_object`	225.221 usmedian 224.219	317.405 usmedian 316.673	380.116 usmedian 380.124	1.41x

FPM One Fetch Per Request

Workload	UserCache	APCu	DeepClone	APCu/UserCache	Workers
`constant_array`	2.292 usmedian 1.500	7.607 usmedian 7.042	6.813 usmedian 5.896	3.32x	5
`route_table_read`	3.910 usmedian 3.542	472.488 usmedian 468.500	476.440 usmedian 482.104	120.85x	5
`large_array`	3.756 usmedian 3.521	276.874 usmedian 278.208	263.452 usmedian 265.270	73.71x	5
`large_string`	5.743 usmedian 3.584	18.456 usmedian 15.271	17.801 usmedian 13.959	3.21x	5
`large_object_graph`	36.849 usmedian 36.230	226.388 usmedian 224.166	231.226 usmedian 235.521	6.14x	5
`metadata_object_read`	101.490 usmedian 94.167	474.141 usmedian 492.604	359.705 usmedian 323.958	4.67x	5
`metadata_object_fetch_mutate`	77.060 usmedian 74.000	419.406 usmedian 430.271	510.993 usmedian 486.750	5.44x	5
`safe_direct_object`	16.376 usmedian 13.729	24.397 usmedian 20.063	28.171 usmedian 25.084	1.49x	5
`spl_collection_object`	9.303 usmedian 8.125	61.867 usmedian 59.500	66.477 usmedian 65.959	6.65x	5
`spl_linked_collection_object`	11.309 usmedian 9.542	67.708 usmedian 65.188	66.433 usmedian 64.980	5.99x	5
`spl_heap_object`	7.317 usmedian 6.063	104.465 usmedian 103.521	110.114 usmedian 108.146	14.28x	5
`carbon_datetime_object`	296.946 usmedian 297.583	605.159 usmedian 590.167	612.603 usmedian 595.834	2.04x	5
`carbon_model_object`	308.572 usmedian 316.979	601.078 usmedian 610.396	687.385 usmedian 687.917	1.95x	5

FPM Hot Read

Workload	UserCache	APCu	DeepClone	APCu/UserCache	Workers
`route_table_read`	0.462 usmedian 0.401	203.533 usmedian 216.544	176.848 usmedian 160.294	440.51x	5
`large_array`	0.223 usmedian 0.212	96.877 usmedian 89.921	97.985 usmedian 90.478	434.99x	5
`large_string`	0.165 usmedian 0.137	8.595 usmedian 9.564	8.967 usmedian 9.570	52.06x	5
`large_object_graph`	0.576 usmedian 0.573	97.342 usmedian 91.601	98.284 usmedian 91.729	169.06x	5
`metadata_object_read`	0.911 usmedian 0.912	189.581 usmedian 173.893	200.635 usmedian 194.952	208.13x	5
`metadata_object_fetch_mutate`	1.028 usmedian 1.031	191.605 usmedian 177.608	202.894 usmedian 188.424	186.33x	5
`safe_direct_object`	0.701 usmedian 0.693	2.710 usmedian 2.688	4.656 usmedian 4.579	3.86x	5
`spl_collection_object`	0.940 usmedian 0.927	22.786 usmedian 22.016	24.844 usmedian 24.100	24.24x	5
`spl_heap_object`	1.427 usmedian 1.418	33.968 usmedian 32.640	36.419 usmedian 34.161	23.81x	5
`carbon_datetime_object`	34.331 usmedian 33.028	209.218 usmedian 190.512	282.133 usmedian 278.857	6.09x	5
`carbon_model_object`	44.108 usmedian 42.354	273.962 usmedian 264.983	354.067 usmedian 357.772	6.21x	5

Resident Payload Probe

Workload	Resident direct access	UserCache fetch + access	Estimated fetch overhead	Resident / UserCache
`constant_array`resident baseline note	0.058 us	0.157 us	0.098 us	0.37x
`route_table_read`resident baseline note	0.101 us	0.191 us	0.090 us	0.53x
`large_array`resident baseline note	0.068 us	0.151 us	0.083 us	0.45x
`large_string`resident baseline note	0.033 us	0.113 us	0.079 us	0.30x

Bulk Read: 32 Keys

Backend	Mean/batch	Median/batch	Mean/key
`user_cache_fetch_multiple`	1.195 us	1.156 us	0.037 us
`user_cache_fetch_loop`	1.986 us	1.969 us	0.062 us
`apcu_fetch_multiple`	9.330 us	9.240 us	0.292 us
`apcu_fetch_loop`	10.252 us	10.257 us	0.320 us

Bulk Read: 128 Keys

Backend	Mean/batch	Median/batch	Mean/key
`user_cache_fetch_multiple`	4.663 us	4.587 us	0.036 us
`user_cache_fetch_loop`	7.933 us	7.930 us	0.062 us
`apcu_fetch_multiple`	39.028 us	38.712 us	0.305 us
`apcu_fetch_loop`	42.742 us	42.411 us	0.334 us

Artifacts

Artifact	Path
CLI repeated read JSON	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/cli-read/user-cache-benchmark-20260701-160044.json`
CLI write JSON	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/cli-write/user-cache-benchmark-20260701-160059.json`
Resident probe JSON	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/resident-payload-probe.json`
FPM one fetch/request JSON	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/fpm-read-once.json`
FPM hot read JSON	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/fpm-read-hot.json`
Bulk read JSON #1	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/bulk-read-32.json`
Bulk read JSON #2	`/workspaces/php-src/php-opcache_user_cache_benchmark_harness/results/nts-clean-20260701T155740Z/bulk-read-128.json`

Workloads

Click a workload name in the result tables to jump to its description. CLI repeated read stores the payload before timing, then measures only fetch() plus the access probe. CLI store repeatedly stores the payload over the configured key space. Resident direct access runs only the access probe against an already-resident payload. FPM rows run the same fetch path through nginx/php-fpm workers. Bulk read primes multiple keys, then measures fetching the whole key set.

Workload	What It Measures	Measured In
`constant_array`Constant array	Small immutable constant-array payload.Mutates fetched copy: no	CLI repeated read, CLI store, Resident direct access, FPM one fetch/request
`route_table_read`Compiled route table read	Framework-shaped compiled route table and URL generator arrays.Mutates fetched copy: no	CLI repeated read, CLI store, Resident direct access, FPM one fetch/request, FPM hot read
`large_array`Large nested array	Larger object-free nested array with repeated scalar leaves.Mutates fetched copy: no	CLI repeated read, CLI store, Resident direct access, FPM one fetch/request, FPM hot read
`large_string`Large immutable string	Large string payload that stresses byte-copy avoidance on repeated reads.Mutates fetched copy: no	CLI repeated read, CLI store, Resident direct access, FPM one fetch/request, FPM hot read
`large_object_graph`Large direct userland-object graph	Large payload object containing many array rows and a child object.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`metadata_object_read`Application metadata object read	Application metadata object with route and service metadata arrays.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`metadata_object_fetch_mutate`Application metadata object fetch and mutate	Fetches a cached userland object graph, then mutates the fetched copy.Mutates fetched copy: yes	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`safe_direct_object`DateTime/DateInterval direct-restore object	DateTimeImmutable, DateTimeZone, and DateInterval safe-direct state.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`spl_collection_object`SPL collection direct-restore object	ArrayObject, ArrayIterator, RecursiveArrayIterator, and SplFixedArray state.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`spl_linked_collection_object`SPL linked-list direct-restore object	SplDoublyLinkedList, SplQueue, and SplStack state.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request
`spl_heap_object`SPL heap direct-restore object	SplMinHeap, SplMaxHeap, and SplPriorityQueue state.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`carbon_datetime_object`Carbon DateTime serializer object	CarbonImmutable/Carbon/CarbonTimeZone object graph used to compare DateTime-derived restore costs.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`carbon_model_object`Model with Carbon properties	Dummy model objects with three Carbon properties: createdAt, updatedAt, and publishedAt.Mutates fetched copy: no	CLI repeated read, CLI store, FPM one fetch/request, FPM hot read
`bulk_read_32_keys`Bulk Read: 32 Keys	Uses the multi-key config payload, primes 32 keys before timing, then repeatedly fetches all keys as a batch. UserCache is measured with fetchMultiple() and with a per-key fetch() loop; APCu is measured with apcu_fetch(array) and with a per-key loop.Measured batches per iteration: 2000	Bulk read
`bulk_read_128_keys`Bulk Read: 128 Keys	Uses the multi-key config payload, primes 128 keys before timing, then repeatedly fetches all keys as a batch. UserCache is measured with fetchMultiple() and with a per-key fetch() loop; APCu is measured with apcu_fetch(array) and with a per-key loop.Measured batches per iteration: 800	Bulk read

Notes

Already-resident data is a baseline

The resident table does not include UserCache store time. It compares direct access to an already-resident payload with fetching a previously stored UserCache entry and running the same access probe. The difference estimates fetch and materialization overhead after the value has already been stored. The primary comparison for UserCache is against APCu or ext-deepclone when reconstructing object-heavy payloads, not against literals already resident in the request.

Slower stores are an expected trade-off for faster reads

Store workloads are shown to make the write-side cost explicit. APCu-style shared caches are usually used for read-heavy paths, where a stored value is read many times. Store throughput is an intentional trade-off in this design, not the metric it is optimized for.