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[release-branch.go1.9] runtime: fall back to small mmaps if we fail to grow reservation

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Right now, if it's possible to grow the arena reservation but
mheap.sysAlloc fails to get 256MB more of memory, it simply fails.
However, on 32-bit we have a fallback path that uses much smaller
mmaps that could take in this situation, but fail to.

This commit fixes mheap.sysAlloc to use a common failure path in case
it can't grow the reservation. On 32-bit, this path includes the
fallback.

Ideally, mheap.sysAlloc would attempt smaller reservation growths
first, but taking the fallback path is a simple change for Go 1.9.

Updates #21044 (fixes one of two issues).

Cherry-pick of CL 51713. Updates #21234.

Change-Id: I1e0035ffba986c3551479d5742809e43da5e7c73
Reviewed-on: https://go-review.googlesource.com/52190
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Austin Clements 2017-07-28 18:06:03 -04:00
parent 7320506bc5
commit 1a6d87d4bf
1 changed files with 5 additions and 1 deletions
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6
src/runtime/malloc.go
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@ -416,7 +416,10 @@ func (h *mheap) sysAlloc(n uintptr) unsafe.Pointer {
var reserved bool
p := uintptr(sysReserve(unsafe.Pointer(h.arena_end), p_size, &reserved))
if p == 0 {
return nil
// TODO: Try smaller reservation
// growths in case we're in a crowded
// 32-bit address space.
goto reservationFailed
}
// p can be just about anywhere in the address
// space, including before arena_end.
@ -476,6 +479,7 @@ func (h *mheap) sysAlloc(n uintptr) unsafe.Pointer {
return unsafe.Pointer(p)
}
reservationFailed:
// If using 64-bit, our reservation is all we have.
if sys.PtrSize != 4 {
return nil