languages/go
languages/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-09-05 16:04:50 +00:00
Code Issues Packages Projects Releases Wiki Activity

runtime: avoid calling adjustpointers unnecessarily

Browse source 
adjustpointers loops over a bitmap.
If the length of that bitmap is zero,
we can skip making the call entirely.
This speeds up stack copying when there are
no pointers present in either args or locals.

name                old time/op  new time/op  delta
StackCopyPtr-8       101ms ± 4%    90ms ± 4%  -10.95%  (p=0.000 n=87+93)
StackCopy-8         80.1ms ± 4%  72.6ms ± 4%   -9.41%  (p=0.000 n=98+100)
StackCopyNoCache-8   121ms ± 3%   113ms ± 3%   -6.57%  (p=0.000 n=98+97)

Change-Id: I7a272e19bc9a14fa3e3318771ebd082dc6247d25
Reviewed-on: https://go-review.googlesource.com/104737
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Josh Bleecher Snyder 2018-04-04 09:24:13 -07:00
parent 533fdfd00e
commit 2e7e57770c
1 changed files with 19 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

32
src/runtime/stack.go
View file

@ -643,24 +643,28 @@ func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
minsize = sys.MinFrameSize
}
if size > minsize {
var bv bitvector
stackmap := (*stackmap)(funcdata(f, _FUNCDATA_LocalsPointerMaps))
if stackmap == nil || stackmap.n <= 0 {
print("runtime: frame ", funcname(f), " untyped locals ", hex(frame.varp-size), "+", hex(size), "\n")
throw("missing stackmap")
}
// Locals bitmap information, scan just the pointers in locals.
if pcdata < 0 || pcdata >= stackmap.n {
// don't know where we are
print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " locals stack map entries for ", funcname(f), " (targetpc=", targetpc, ")\n")
throw("bad symbol table")
// If nbit == 0, there's no work to do.
if stackmap.nbit > 0 {
// Locals bitmap information, scan just the pointers in locals.
if pcdata < 0 || pcdata >= stackmap.n {
// don't know where we are
print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " locals stack map entries for ", funcname(f), " (targetpc=", targetpc, ")\n")
throw("bad symbol table")
}
bv := stackmapdata(stackmap, pcdata)
size = uintptr(bv.n) * sys.PtrSize
if stackDebug >= 3 {
print(" locals ", pcdata, "/", stackmap.n, " ", size/sys.PtrSize, " words ", bv.bytedata, "\n")
}
adjustpointers(unsafe.Pointer(frame.varp-size), &bv, adjinfo, f)
} else if stackDebug >= 3 {
print(" no locals to adjust\n")
}
bv = stackmapdata(stackmap, pcdata)
size = uintptr(bv.n) * sys.PtrSize
if stackDebug >= 3 {
print(" locals ", pcdata, "/", stackmap.n, " ", size/sys.PtrSize, " words ", bv.bytedata, "\n")
}
adjustpointers(unsafe.Pointer(frame.varp-size), &bv, adjinfo, f)
}
// Adjust saved base pointer if there is one.
@ -707,7 +711,9 @@ func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
if stackDebug >= 3 {
print(" args\n")
}
adjustpointers(unsafe.Pointer(frame.argp), &bv, adjinfo, funcInfo{})
if bv.n > 0 {
adjustpointers(unsafe.Pointer(frame.argp), &bv, adjinfo, funcInfo{})
}
}
return true
}