update api and doc

Author: chenyu-jiang

README.md

@@ -17,10 +17,13 @@ To extract kernel activities and NVTX annotated regions (e.g. [torch.cuda.nvtx.r
 python3 nsys2json.py <nsys_sqlite_file> -o <output_json>
 ```
 
-To filter out only kernel activities or NVTX annotated regions, use:
+To filter out kernel activities or NVTX annotated regions, use:
 ```bash
--activity-type {kernel,nvtx}
+-activity-type {kernel, nvtx-cpu, nvtx-kernel}
 ```
+* `kernel`: Raw CUDA kernel activities
+* `nvtx-cpu`: NVTX annotated regions on CPU threads
+* `nvtx-kernel`: NVTX annotated regions, but calculate the start and end time from CUDA kernel activities launched within the region
 
 To filter NVTX regions based on name, use:
 ```bash

nsys2json.py

@@ -306,7 +306,7 @@ def nsys2json():
     for activity in args.activity_type:
         if activity == "kernel":
             parse_cupti_kernel_events(conn, strings, traceEvents)
-        elif activity == "nvtx":
+        elif activity == "nvtx-cpu":
             parse_nvtx_events(conn, traceEvents, event_prefix=args.nvtx_event_prefix, color_scheme=args.nvtx_color_scheme)
         elif activity == "nvtx-kernel":
             parse_nvtx_kernel_events(conn, strings, traceEvents, event_prefix=args.nvtx_event_prefix, color_scheme=args.nvtx_color_scheme)