:sig
DValue request_perf()

:params
return value : performance snapshot for the active request/workspace

:see
>sys
>time_precise

:content
Returns a DValue with timing and process metadata such as worker pid, parent pid, request count, request start times, native dispatch, workspace setup and birth, context application, guest execution, and hostcall timing. `accept_us` is divided into `transport_params_us` (FastCGI begin through the end of parameters), `transport_input_us` (parameters through the end of input), and `handler_queue_us` (input close through handler entry). This distinguishes upstream request delivery from work inside the UCE handler.

Hostcall totals include component resolution. When `WASM_PROFILE_HOSTCALL_CPU=1`, `hostcall_cpu_us` separates thread CPU from hostcall wall time and each bounded `hostcall_operations` item includes the same `cpu_us` attribution. This diagnostic is off by default because sampling thread CPU around every hostcall adds hot-path cost; `hostcall_cpu_profiled` identifies whether the current request used it, and disabled counters remain zero. `WASM_PROFILE_THREAD_RUNTIME=1` adds one bounded kernel thread snapshot per request: user/system CPU, voluntary/involuntary context switches, minor/major faults, and start/end logical CPU plus migration state. `thread_runtime_profiled` identifies the opt-in diagnostic; its counters are absent when disabled. MySQL, memcache, and component resolution also expose their own count and microsecond fields. Workspace setup, birth, and context application expose matching wall and thread-CPU microseconds. `execution_cpu_us` is the remaining workspace thread CPU through the snapshot after those three phases. `unit_module_operations` is a source-root-relative list of up to 32 unit loads. Each item attributes module lookup/read/parse/build/classification plus allocation, import construction, symbol resolution, instantiation, and initialization; no caller-supplied paths are exposed. `mysql_operations` is an ordered, query-text-free list of up to 64 logical MySQL operations and their microsecond durations. A connect operation also identifies its source as `new`, cross-request `worker`, or same-request `request`; the corresponding `mysql_connection_open_count`, `mysql_connection_reuse_count`, and `mysql_request_pool_hit_count` fields provide totals. `mysql_operations_dropped` reports any overflow. The profiling hostcall itself is excluded from those totals so repeated snapshots remain comparable.

Component resolution is divided into `component_path_us`, `component_artifact_us`, `component_load_us`, and `component_link_us`. These aggregate path resolution, artifact readiness/freshness, Wasmtime side-module loading, and exported-handler lookup/table placement without exposing source paths.

Successful first loads within the request are counted by `unit_load_count` and divided into `unit_module_us`, `unit_allocate_us`, `unit_import_us`, `unit_instantiate_us`, and `unit_initialize_us`. These cover compiled-module lookup, guest memory/table allocation, import construction, Wasmtime instantiation, and relocations/constructors/request binding. `entry_unit_load_count` and `entry_unit_materialize_us` isolate the initial page/CLI unit; `dynamic_include_load_count` and `dynamic_include_materialize_us` isolate side units first requested through `component()`. The per-unit bounded list adds `kind` (`entry` or `component`) and `materialize_us`, the inclusive host-side time from module acquisition through request binding. Repeated handlers from an already loaded unit are excluded.

`unit_module_cache_hit_count` and `unit_module_cache_miss_count` divide module loads by the worker's compiled-module cache. A miss is further identified by `unit_module_serialized_cache_hit_count` when Wasmtime deserializes the current `.cwasm`; `unit_module_compile_count` means it fell back to compiling the `.wasm`. `unit_module_lookup_us`, `unit_module_read_us`, `unit_module_read_bytes`, `unit_module_parse_us`, `unit_module_compile_us`, and `unit_module_classify_us` divide `unit_module_us` into artifact stat/cache lookup, wasm metadata/full-artifact read volume, custom-section parse, deserialize-or-compile, and immutable import classification. A current serialized-module hit scans only section headers and the `dylink.0`/`uce.abi` payloads; compilation fallback reads the complete wasm. The phase sum can be below the total because allocation and cache publication overhead remain in the aggregate.

`unit_symbol_resolve_count` and `unit_symbol_resolve_us` isolate function and data symbol lookup within `unit_import_us`. The remainder of import time covers import-vector construction, Wasmtime Globals, GOT function table placement, and related bindings.

The request log's `wasm-ready`, `wasm`, `workspace`, `invoke`, `collect`, and `post` fields complete the timing boundary after this in-page snapshot: compiled-artifact readiness before backend entry, native backend wall time, complete workspace wall time, entry invocation, guest-output/meta collection, and native response assembly after the backend. They do not expose request data. This distinction is useful when a completed FastCGI request takes longer than the page's mid-render `request_perf()` snapshot.

Workspace birth is subdivided into `birth_policy_us`, `birth_import_us`, `birth_instantiate_us`, `birth_exports_us`, and `birth_initialize_us`. Request-context transfer reports `context_bytes`, `context_encode_us`, `context_allocate_us`, `context_write_us`, `context_guest_apply_us`, and `context_free_us`. These bounded aggregate fields expose sizes and timing only, never request values.

Wasm FastCGI workers retain up to `MYSQL_PERSISTENT_POOL_SIZE` credential-keyed MySQL connections (default `8`; set `0` to disable). UCE calls the client library's connection-reset operation before another request receives a cached connection, clearing transactions, temporary tables, session variables, and selected databases while avoiding a new authentication handshake. Same-request leases continue to share state until request cleanup.

:example
DValue perf = request_perf();
print(perf.get_type_name() != "invalid" ? "captured a timing snapshot" : "no data", "\n");
