From 3e214e5693ff8df58011db8250cdd8874a63ea17 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Fri, 16 Feb 2018 17:45:21 -0500 Subject: [PATCH] runtime: simplify bulkBarrierPreWrite Currently, bulkBarrierPreWrite uses inheap to decide whether the destination is in the heap or whether to check for stack or global data. However, this isn't the best question to ask. Instead, get the span directly and query its state. This lets us directly determine whether this might be a global, or is stack memory, or is heap memory. At this point, inheap is no longer used in the hot path, so drop it from the must-be-inlined list and substitute spanOf. This will help in a circuitous way with #23862, since fixing that is going to push inheap very slightly over the inline-able threshold on a few platforms. Change-Id: I5360fc1181183598502409f12979899e1e4d45f7 Reviewed-on: https://go-review.googlesource.com/95495 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Rick Hudson --- src/cmd/compile/internal/gc/inl_test.go | 2 +- src/runtime/mbitmap.go | 16 +++++++++------- 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/src/cmd/compile/internal/gc/inl_test.go b/src/cmd/compile/internal/gc/inl_test.go index 3e6da2ed7b..a937c15432 100644 --- a/src/cmd/compile/internal/gc/inl_test.go +++ b/src/cmd/compile/internal/gc/inl_test.go @@ -78,10 +78,10 @@ func TestIntendedInlining(t *testing.T) { "heapBits.morePointers", "heapBits.next", "heapBitsForAddr", - "inheap", "markBits.isMarked", "muintptr.ptr", "puintptr.ptr", + "spanOf", "spanOfUnchecked", "(*gcWork).putFast", "(*gcWork).tryGetFast", diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go index 0027bc9c05..3dc22e8458 100644 --- a/src/runtime/mbitmap.go +++ b/src/runtime/mbitmap.go @@ -574,13 +574,7 @@ func bulkBarrierPreWrite(dst, src, size uintptr) { if !writeBarrier.needed { return } - if !inheap(dst) { - gp := getg().m.curg - if gp != nil && gp.stack.lo <= dst && dst < gp.stack.hi { - // Destination is our own stack. No need for barriers. - return - } - + if s := spanOf(dst); s == nil { // If dst is a global, use the data or BSS bitmaps to // execute write barriers. for _, datap := range activeModules() { @@ -596,6 +590,14 @@ func bulkBarrierPreWrite(dst, src, size uintptr) { } } return + } else if s.state != _MSpanInUse || dst < s.base() || s.limit <= dst { + // dst was heap memory at some point, but isn't now. + // It can't be a global. It must be either our stack, + // or in the case of direct channel sends, it could be + // another stack. Either way, no need for barriers. + // This will also catch if dst is in a freed span, + // though that should never have. + return } buf := &getg().m.p.ptr().wbBuf