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, 4 insertions, 6 deletions

diff --git a/libgo/go/runtime/heapdump.go b/libgo/go/runtime/heapdump.go
index 3aa9e8a..b0506a8 100644
--- a/libgo/go/runtime/heapdump.go
+++ b/libgo/go/runtime/heapdump.go
@@ -437,17 +437,15 @@ func dumpmemstats() {
 	dumpint(uint64(memstats.numgc))
 }
 
-func dumpmemprof_callback(b *bucket, nstk uintptr, pstk *location, size, allocs, frees uintptr) {
-	stk := (*[100000]location)(unsafe.Pointer(pstk))
+func dumpmemprof_callback(b *bucket, nstk uintptr, pstk *uintptr, size, allocs, frees uintptr) {
+	stk := (*[100000]uintptr)(unsafe.Pointer(pstk))
 	dumpint(tagMemProf)
 	dumpint(uint64(uintptr(unsafe.Pointer(b))))
 	dumpint(uint64(size))
 	dumpint(uint64(nstk))
 	for i := uintptr(0); i < nstk; i++ {
-		pc := stk[i].pc
-		fn := stk[i].function
-		file := stk[i].filename
-		line := stk[i].lineno
+		pc := stk[i]
+		fn, file, line, _ := funcfileline(pc, -1)
 		if fn == "" {
 			var buf [64]byte
 			n := len(buf)