libgo: reduce overhead for memory/block/mutex profiling

    
    Revise the gccgo version of memory/block/mutex profiling to reduce
    runtime overhead. The main change is to collect raw stack traces while
    the profile is on line, then post-process the stacks just prior to the
    point where we are ready to use the final product. Memory profiling
    (at a very low sampling rate) is enabled by default, and the overhead
    of the symbolization / DWARF-reading from backtrace_full was slowing
    things down relative to the main Go runtime.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/171497

From-SVN: r271172

1 files changed, 1 insertions, 0 deletions

diff --git a/libgo/runtime/runtime.h b/libgo/runtime/runtime.h
index 9506e3d..71c1a3e 100644
--- a/libgo/runtime/runtime.h
+++ b/libgo/runtime/runtime.h
@@ -485,6 +485,7 @@ struct funcfileline_return
   String retfn;
   String retfile;
   intgo retline;
+  intgo retframes;
 };
 
 struct funcfileline_return