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[dev.link] cmd/link: only allow heap area to grow to 10MB

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With CL 228782, we've removed file I/O, but we're growing the memory too
much. This change will periodically flush the heap area to the mmapped
area (if possible).

Change-Id: I1622c738ee5a1a6d02bff5abb0a5751caf8095c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/229439
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Jeremy Faller 2020-04-22 12:13:33 -04:00
parent 00723603eb
commit 7466cad9c4
1 changed files with 28 additions and 14 deletions
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42
src/cmd/link/internal/ld/outbuf.go
View File

@ -113,7 +113,9 @@ func (out *OutBuf) Close() error {
return viewCloseError
}
if out.isMmapped() {
return out.Munmap()
out.copyHeap()
out.munmap()
return nil
}
if out.f == nil {
return nil
@ -135,26 +137,33 @@ func (out *OutBuf) isMmapped() bool {
return len(out.buf) != 0
}
// Munmap cleans up all the output buffer.
func (out *OutBuf) Munmap() error {
wasMapped := out.isMmapped()
// copyHeap copies the heap to the mmapped section of memory, returning true if
// a copy takes place.
func (out *OutBuf) copyHeap() bool {
if !out.isMmapped() { // only valuable for mmapped OutBufs.
return false
}
if out.isView {
panic("can't copyHeap a view")
}
bufLen := len(out.buf)
heapLen := len(out.heap)
total := uint64(bufLen + heapLen)
if wasMapped {
out.munmap()
if heapLen != 0 {
if err := out.Mmap(total); err != nil {
return err
}
copy(out.buf[bufLen:], out.heap[:heapLen])
out.heap = nil
out.munmap()
out.munmap()
if heapLen != 0 {
if err := out.Mmap(total); err != nil {
panic(err)
}
copy(out.buf[bufLen:], out.heap[:heapLen])
out.heap = out.heap[:0]
}
return nil
return true
}
// maxOutBufHeapLen limits the growth of the heap area.
const maxOutBufHeapLen = 10 << 20
// writeLoc determines the write location if a buffer is mmaped.
// We maintain two write buffers, an mmapped section, and a heap section for
// writing. When the mmapped section is full, we switch over the heap memory
@ -176,6 +185,11 @@ func (out *OutBuf) writeLoc(lenToWrite int64) (int64, []byte) {
if out.isView {
panic("cannot write to heap in parallel")
}
// See if our heap would grow to be too large, and if so, copy it to the end
// of the mmapped area.
if heapLen > maxOutBufHeapLen && out.copyHeap() {
heapPos, heapLen, lenNeeded = 0, 0, lenToWrite
}
out.heap = append(out.heap, make([]byte, lenNeeded-heapLen)...)
}
return heapPos, out.heap