chrome_main_thread_hotspots
Identify top Chrome main-thread tasks causing jank or slow load by wall duration, with filtering by process, page load phase, and duration threshold.
Instructions
Top Chrome main-thread tasks by wall duration: id, ts, name, task_type, thread_name, process_name, upid, pid, nullable machine_id, dur_ms, overlap_dur_ms, full_task_cpu_pct/full_task_thread_dur_ms, overlap_cpu_pct/overlap_thread_dur_ms; legacy cpu_pct/thread_dur_ms are full-task. Uses chrome.tasks, thread.is_main_thread = 1, and Chrome's Cr*Main fallback. Pass a returned id to slice_descendants_breakdown for child-slice breakdowns.
Use when: investigating responsiveness, scroll/load stalls, CPU vs wall time, or one renderer.
Don't use for: non-Chrome traces (will error). For background (non-main) thread tasks, drop to execute_sql against chrome.tasks directly.
Parameters (all optional):
process_name/pid/machine_id/upid: scope to one process/type. Preferupid; addmachine_idto disambiguate multi-machinepids. All filters AND.page_load_id/navigation_id/phase: scope to a page-load window. IDs matchchrome_page_loads.idand.navigation_idrespectively and are mutually exclusive.phase:navigation_to_fcp,navigation_to_load,dcl_to_fcp,fcp_to_load. If an id is set withoutphase, defaults tonavigation_to_fcp; phase-only uses the latest page load.start_ts_ns/end_ts_ns: raw trace timestamp bounds in nanoseconds (end_ts_nsexclusive); aliasesstart_ts/end_tsare accepted; intersect page-load windows.overlap_dur_msis clipped to that window.min_dur_ms: minimum full-task duration, or clipped overlap duration when a window is set. Defaults to 16 ms. Pass 0 for all positive-overlap tasks.limit: max rows (default 100, capped at 5000). Must be > 0 if set.max_string_len: optional cap for returned string cells. Unset preserves full strings for precision. Must be > 0 if set.
Output: metadata-first JSON preserving columns / rows; truncated=true means an extra-row probe found more rows; string_truncated=true means cell text was shortened.
Empty result: no detected main-thread tasks exceeded min_dur_ms at the selected process/window threshold, or the trace uses non-standard main-thread names outside the Cr*Main fallback.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| pid | No | Optional pid filter — the OS-level process ID (visible in Task Manager). Get pid from `list_processes`. ANDs with the other filters when set. Note: pids can be recycled within a long trace; prefer `upid` when precision matters. Accepts both numbers and numeric strings. | |
| upid | No | Optional upid filter — the trace-internal Unique Process ID assigned by trace_processor (also from `list_processes`). Always uniquely identifies one process within a trace, even if the OS recycled its pid. Use this to disambiguate same-named or pid-recycled processes; ANDs with the other filters when set. Accepts both numbers and numeric strings. | |
| limit | No | Optional max rows to return. Defaults to 100 and is capped at 5000 to match `execute_sql`. Lower values keep responses short; higher values surface long tails of mid-duration tasks. Accepts both numbers and numeric strings. | |
| phase | No | Optional page-load phase window. If set without `page_load_id` or `navigation_id`, uses the latest page load in the trace. Values: navigation_to_fcp, navigation_to_load, dcl_to_fcp, fcp_to_load. | |
| trace_id | No | Optional trace id returned by `load_trace`. Omit to use the active trace. | |
| end_ts_ns | No | Optional raw trace timestamp upper bound in nanoseconds, exclusive. This uses the same unit as the returned `ts` column. ANDs with any page-load window. | |
| machine_id | No | Optional machine id filter for multi-machine traces when the trace schema has `process.machine_id`. ANDs with pid/process filters and disambiguates same pid values on different machines. Accepts numbers and numeric strings. | |
| min_dur_ms | No | Optional minimum task duration in milliseconds. Defaults to 16 ms (one 60 Hz frame budget). Pass 0 to see ALL main-thread tasks; raise to e.g. 33 (30 Hz) or 100 to focus on the worst stutters. Must be a finite non-negative number. Accepts both numbers and numeric strings. | |
| start_ts_ns | No | Optional raw trace timestamp lower bound in nanoseconds. This uses the same unit as the returned `ts` column. ANDs with any page-load window. | |
| page_load_id | No | Optional page-load id used to scope tasks to one navigation phase. Matches `chrome_page_loads.id`. Mutually exclusive with `navigation_id`. If set without `phase`, defaults to `navigation_to_fcp`. | |
| process_name | No | Optional process-name filter (e.g. "Renderer", "Browser", "GPU Process"). Useful to scope to one process type without picking a specific instance. | |
| navigation_id | No | Optional Chrome navigation id used to scope tasks to one navigation phase. Matches `chrome_page_loads.navigation_id`. Mutually exclusive with `page_load_id`. If set without `phase`, defaults to `navigation_to_fcp`. | |
| max_string_len | No | Optional per-string-cell character cap applied to returned rows only. Unset preserves full strings for precision; accepts both numbers and numeric strings. Must be > 0 when set. |