mirror of
https://github.com/golang/go
synced 2024-10-03 06:21:21 -06:00
22a7f2a14d
because free needs to mark the block as freed to coordinate with the garbage collector. (in C++ free can blindly put the block on the free list, no questions asked, so the cache saves some work.) R=iant CC=golang-dev https://golang.org/cl/206069
61 lines
1.7 KiB
C
61 lines
1.7 KiB
C
// 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.
|
|
|
|
// Free(v) must be able to determine the MSpan containing v.
|
|
// The MHeapMap is a 3-level radix tree mapping page numbers to MSpans.
|
|
//
|
|
// NOTE(rsc): On a 32-bit platform (= 20-bit page numbers),
|
|
// we can swap in a 2-level radix tree.
|
|
//
|
|
// NOTE(rsc): We use a 3-level tree because tcmalloc does, but
|
|
// having only three levels requires approximately 1 MB per node
|
|
// in the tree, making the minimum map footprint 3 MB.
|
|
// Using a 4-level tree would cut the minimum footprint to 256 kB.
|
|
// On the other hand, it's just virtual address space: most of
|
|
// the memory is never going to be touched, thus never paged in.
|
|
|
|
typedef struct MHeapMapNode2 MHeapMapNode2;
|
|
typedef struct MHeapMapNode3 MHeapMapNode3;
|
|
|
|
enum
|
|
{
|
|
// 64 bit address - 12 bit page size = 52 bits to map
|
|
MHeapMap_Level1Bits = 18,
|
|
MHeapMap_Level2Bits = 18,
|
|
MHeapMap_Level3Bits = 16,
|
|
|
|
MHeapMap_TotalBits =
|
|
MHeapMap_Level1Bits +
|
|
MHeapMap_Level2Bits +
|
|
MHeapMap_Level3Bits,
|
|
|
|
MHeapMap_Level1Mask = (1<<MHeapMap_Level1Bits) - 1,
|
|
MHeapMap_Level2Mask = (1<<MHeapMap_Level2Bits) - 1,
|
|
MHeapMap_Level3Mask = (1<<MHeapMap_Level3Bits) - 1,
|
|
};
|
|
|
|
struct MHeapMap
|
|
{
|
|
void *(*allocator)(uintptr);
|
|
MHeapMapNode2 *p[1<<MHeapMap_Level1Bits];
|
|
};
|
|
|
|
struct MHeapMapNode2
|
|
{
|
|
MHeapMapNode3 *p[1<<MHeapMap_Level2Bits];
|
|
};
|
|
|
|
struct MHeapMapNode3
|
|
{
|
|
MSpan *s[1<<MHeapMap_Level3Bits];
|
|
};
|
|
|
|
void MHeapMap_Init(MHeapMap *m, void *(*allocator)(uintptr));
|
|
bool MHeapMap_Preallocate(MHeapMap *m, PageID k, uintptr npages);
|
|
MSpan* MHeapMap_Get(MHeapMap *m, PageID k);
|
|
MSpan* MHeapMap_GetMaybe(MHeapMap *m, PageID k);
|
|
void MHeapMap_Set(MHeapMap *m, PageID k, MSpan *v);
|
|
|
|
|