From 40712a962573a9ad987c71ba2cb24e6d430b559d Mon Sep 17 00:00:00 2001

From: Austin Clements <[email protected]>

Date: Fri, 19 Aug 2016 16:03:14 -0400

Subject: [PATCH 15/38] [release-branch.go1.7] runtime: fix check for vacuous

 page boundary rounding again

The previous fix for this, commit 336dad2a, had everything right in

the commit message, but reversed the test in the code. Fix the test in

the code.

This reversal effectively disabled the scavenger on large page systems

*except* in the rare cases where this code was originally wrong, which

is why it didn't obviously show up in testing.

Fixes #16644. Again. :(

Change-Id: I27cce4aea13de217197db4b628f17860f27ce83e

Reviewed-on: https://go-review.googlesource.com/27402

Run-TryBot: Austin Clements <[email protected]>

Reviewed-by: Brad Fitzpatrick <[email protected]>

Reviewed-on: https://go-review.googlesource.com/28631

Run-TryBot: Chris Broadfoot <[email protected]>

---

 src/runtime/mheap.go | 4 +++-

 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go

index db60f7a..8db2fcc 100644

--- a/src/runtime/mheap.go

+++ b/src/runtime/mheap.go

@@ -917,7 +917,9 @@ func scavengelist(list *mSpanList, now, limit uint64) uintptr {

 				// more memory than we want.)

 				start = (start + sys.PhysPageSize - 1) &^ (sys.PhysPageSize - 1)

 				end &^= sys.PhysPageSize - 1

-				if start == end {

+				if end <= start {

+					// start and end don't span a

+					// whole physical page.

 					continue

 				}

 			}

-- 

2.7.4