qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-19 14:54:43 -07:00
Code Releases Activity

runtime: simplify and cleanup mallocinit

Browse Source 
mallocinit has evolved organically. Make a pass to clean it up in
various ways:

1. Merge the computation of spansSize and bitmapSize. These were
   computed on every loop iteration of two different loops, but always
   have the same value, which can be derived directly from _MaxMem.
   This also avoids over-reserving these on MIPS, were _MaxArena32 is
   larger than _MaxMem.

2. Remove the ulimit -v logic. It's been disabled for many releases
   and the dead code paths to support it are even more wrong now than
   they were when it was first disabled, since now we *must* reserve
   spans and bitmaps for the full address space.

3. Make it clear that we're using a simple linear allocation to lay
   out the spans, bitmap, and arena spaces. Previously there were a
   lot of redundant pointer computations. Now we just bump p1 up as we
   reserve the spaces.

In preparation for #18651.

Updates #5049 (respect ulimit).

Change-Id: Icbe66570d3a7a17bea227dc54fb3c4978b52a3af
Reviewed-on: https://go-review.googlesource.com/35252
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Austin Clements 2017-01-13 14:19:52 -05:00
parent efb5eae3cf
commit 1cc24690b8
1 changed files with 18 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
src/runtime/malloc.go
View File

@ -242,18 +242,21 @@ func mallocinit() {
throw("bad system page size")
}
var p, bitmapSize, spansSize, pSize, limit uintptr
// The auxiliary regions start at p and are laid out in the
// following order: spans, bitmap, arena.
var p, pSize uintptr
var reserved bool
// limit = runtime.memlimit();
// See https://golang.org/issue/5049
// TODO(rsc): Fix after 1.1.
limit = 0
// The spans array holds one *mspan per _PageSize of arena.
var spansSize uintptr = (_MaxMem + 1) / _PageSize * sys.PtrSize
spansSize = round(spansSize, _PageSize)
// The bitmap holds 2 bits per word of arena.
var bitmapSize uintptr = (_MaxMem + 1) / (sys.PtrSize * 8 / 2)
bitmapSize = round(bitmapSize, _PageSize)
// Set up the allocation arena, a contiguous area of memory where
// allocated data will be found. The arena begins with a bitmap large
// enough to hold 2 bits per allocated word.
if sys.PtrSize == 8 && (limit == 0 || limit > 1<<30) {
// allocated data will be found.
if sys.PtrSize == 8 {
// On a 64-bit machine, allocate from a single contiguous reservation.
// 512 GB (MaxMem) should be big enough for now.
//
@ -284,9 +287,7 @@ func mallocinit() {
// translation buffers, the user address space is limited to 39 bits
// On darwin/arm64, the address space is even smaller.
arenaSize := round(_MaxMem, _PageSize)
bitmapSize = arenaSize / (sys.PtrSize * 8 / 2)
spansSize = arenaSize / _PageSize * sys.PtrSize
spansSize = round(spansSize, _PageSize)
pSize = bitmapSize + spansSize + arenaSize + _PageSize
for i := 0; i <= 0x7f; i++ {
switch {
case GOARCH == "arm64" && GOOS == "darwin":
@ -296,7 +297,6 @@ func mallocinit() {
default:
p = uintptr(i)<<40 | uintptrMask&(0x00c0<<32)
}
pSize = bitmapSize + spansSize + arenaSize + _PageSize
p = uintptr(sysReserve(unsafe.Pointer(p), pSize, &reserved))
if p != 0 {
break
@ -327,15 +327,6 @@ func mallocinit() {
}
for _, arenaSize := range arenaSizes {
bitmapSize = (_MaxArena32 + 1) / (sys.PtrSize * 8 / 2)
spansSize = (_MaxArena32 + 1) / _PageSize * sys.PtrSize
if limit > 0 && arenaSize+bitmapSize+spansSize > limit {
bitmapSize = (limit / 9) &^ ((1 << _PageShift) - 1)
arenaSize = bitmapSize * 8
spansSize = arenaSize / _PageSize * sys.PtrSize
}
spansSize = round(spansSize, _PageSize)
// SysReserve treats the address we ask for, end, as a hint,
// not as an absolute requirement. If we ask for the end
// of the data segment but the operating system requires
@ -361,18 +352,21 @@ func mallocinit() {
// so SysReserve can give us a PageSize-unaligned pointer.
// To overcome this we ask for PageSize more and round up the pointer.
p1 := round(p, _PageSize)
pSize -= p1 - p
spansStart := p1
mheap_.bitmap = p1 + spansSize + bitmapSize
p1 += spansSize
mheap_.bitmap = p1 + bitmapSize
p1 += bitmapSize
if sys.PtrSize == 4 {
// Set arena_start such that we can accept memory
// reservations located anywhere in the 4GB virtual space.
mheap_.arena_start = 0
} else {
mheap_.arena_start = p1 + (spansSize + bitmapSize)
mheap_.arena_start = p1
}
mheap_.arena_end = p + pSize
mheap_.arena_used = p1 + (spansSize + bitmapSize)
mheap_.arena_used = p1
mheap_.arena_reserved = reserved
if mheap_.arena_start&(_PageSize-1) != 0 {