blob: 438c9875135f4f80976ade0e9c2004af9cde958e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Malloc small size classes.
//
// See malloc.go for overview.
// See also mksizeclasses.go for how we decide what size classes to use.
package runtime
// sizeToClass(0 <= n <= MaxSmallSize) returns the size class,
// 1 <= sizeclass < NumSizeClasses, for n.
// Size class 0 is reserved to mean "not small".
//
// The sizeToClass lookup is implemented using two arrays,
// one mapping sizes <= 1024 to their class and one mapping
// sizes >= 1024 and <= MaxSmallSize to their class.
// All objects are 8-aligned, so the first array is indexed by
// the size divided by 8 (rounded up). Objects >= 1024 bytes
// are 128-aligned, so the second array is indexed by the
// size divided by 128 (rounded up). The arrays are constants
// in sizeclass.go generated by mksizeclass.go.
func sizeToClass(size uint32) uint32 {
if size > _MaxSmallSize {
throw("invalid size")
}
if size > smallSizeMax-8 {
return uint32(size_to_class128[(size-smallSizeMax+largeSizeDiv-1)/largeSizeDiv])
}
return uint32(size_to_class8[(size+smallSizeDiv-1)/smallSizeDiv])
}
// Returns size of the memory block that mallocgc will allocate if you ask for the size.
func roundupsize(size uintptr) uintptr {
if size < _MaxSmallSize {
if size <= smallSizeMax-8 {
return uintptr(class_to_size[size_to_class8[(size+smallSizeDiv-1)/smallSizeDiv]])
} else {
return uintptr(class_to_size[size_to_class128[(size-smallSizeMax+largeSizeDiv-1)/largeSizeDiv]])
}
}
if size+_PageSize < size {
return size
}
return round(size, _PageSize)
}
|
