Add note on external profiler activation.

post/2024-04-26-cuda_5.2_5.3.md

@@ -72,6 +72,29 @@ Host-side activity:
 └──────────┴────────────┴───────┴─────────────────────────────────────┴─────────────────────────┘
 ```
 
+It is also not required anymore to specify `external=true` when using `CUDA.@profile` in
+combination with a tool like NSight Systems, as CUDA.jl will automatically detect the
+presence of an external profiler:
+
+```julia-repl
+shell> nsys launch julia
+
+# warm-up
+julia> CuArray([1]).+1
+1-element CuArray{Int64, 1, CUDA.Mem.DeviceBuffer}:
+ 2
+
+julia> CUDA.@profile CuArray([1]).+1
+[ Info: This Julia session is already being profiled; defaulting to the external profiler.
+Capture range started in the application.
+Capture range ended in the application.
+Generating '/tmp/nsys-report-c42f.qdstrm'
+[1/1] [========================100%] report1.nsys-rep
+```
+
+In case that detection fails, the `external` keyword argument remains available (but do file
+an issue).
+
 
 ## Kernel launch debugging