cmd/trace: force GC occassionally
to return memory to the OS after completing potentially
large operations.
Update #21870
Sys went down to 3.7G
$ DEBUG_MEMORY_USAGE=1 go tool trace trace.out
2018/03/07 09:35:52 Parsing trace...
after parsing trace
Alloc:
3385754360 Bytes
Sys:
3662047864 Bytes
HeapReleased: 0 Bytes
HeapSys:
3488907264 Bytes
HeapInUse:
3426549760 Bytes
HeapAlloc:
3385754360 Bytes
Enter to continue...
2018/03/07 09:36:09 Splitting trace...
after spliting trace
Alloc:
3238309424 Bytes
Sys:
3684410168 Bytes
HeapReleased: 0 Bytes
HeapSys:
3488874496 Bytes
HeapInUse:
3266461696 Bytes
HeapAlloc:
3238309424 Bytes
Enter to continue...
2018/03/07 09:36:39 Opening browser. Trace viewer is listening on http://100.101.224.241:12345
after httpJsonTrace
Alloc:
3000633872 Bytes
Sys:
3693978424 Bytes
HeapReleased: 0 Bytes
HeapSys:
3488743424 Bytes
HeapInUse:
3030966272 Bytes
HeapAlloc:
3000633872 Bytes
Enter to continue...
Change-Id: I56f64cae66c809cbfbad03fba7bd0d35494c1d04
Reviewed-on: https://go-review.googlesource.com/92376
Reviewed-by: Peter Weinberger <pjw@google.com>