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[release-branch.go1.13] runtime: scavenge on growth instead of inline with allocation 

Inline scavenging causes significant performance regressions in tail
latency for k8s and has relatively little benefit for RSS footprint.

We disabled inline scavenging in Go 1.12.5 (CL 174102) as well, but
we thought other changes in Go 1.13 had mitigated the issues with
inline scavenging. Apparently we were wrong.

This CL switches back to only doing foreground scavenging on heap
growth, rather than doing it when allocation tries to allocate from
scavenged space.

Fixes #34556

Change-Id: I1f5df44046091f0b4f89fec73c2cde98bf9448cb
Reviewed-on: https://go-review.googlesource.com/c/go/+/183857
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
(cherry picked from commit eb96f8a574)
Reviewed-on: https://go-review.googlesource.com/c/go/+/198486
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Andrew Bonventre <andybons@golang.org>
This commit is contained in:
Michael Anthony Knyszek 2019-06-25 19:06:57 +00:00 committed by Andrew Bonventre
parent cd951aeec4
commit 66b8787f6b
1 changed files with 4 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/runtime/mheap.go
View File

@ -1227,16 +1227,6 @@ HaveSpan:
// heap_released since we already did so earlier.
sysUsed(unsafe.Pointer(s.base()), s.npages<<_PageShift)
s.scavenged = false
// Since we allocated out of a scavenged span, we just
// grew the RSS. Mitigate this by scavenging enough free
// space to make up for it but only if we need to.
//
// scavengeLocked may cause coalescing, so prevent
// coalescing with s by temporarily changing its state.
s.state = mSpanManual
h.scavengeIfNeededLocked(s.npages * pageSize)
s.state = mSpanFree
}
h.setSpans(s.base(), npage, s)
@ -1312,6 +1302,10 @@ func (h *mheap) grow(npage uintptr) bool {
//
// h must be locked.
func (h *mheap) growAddSpan(v unsafe.Pointer, size uintptr) {
// Scavenge some pages to make up for the virtual memory space
// we just allocated, but only if we need to.
h.scavengeIfNeededLocked(size)
s := (*mspan)(h.spanalloc.alloc())
s.init(uintptr(v), size/pageSize)
h.setSpans(s.base(), s.npages, s)