README
¶
NAME
allocator - malloc(3) like memory allocator
DESCRIPTION
Allocator simulates malloc(3) like memory management with minimal API:
type Heap interface {
Malloc(size int) (address int, err error)
Free(address int)
}
It manages a pre-allocated block of bytes to simulate memory obtained from the Kernel via mmap(2) or brk(2).
Free List
The allocator uses implicit free list. The managed memory consists of blocks with header and payload. The header holds block size and flags to indicate whether the block is allocated or free. The payload is actual address space returned to the use from Malloc().
Coalesce
The allocator supports following strategies to coalesce free spacea after Free() call to reduce fragmentation:
-
noop: disable coalesce.
-
forward: only coalesce next blocks started from the released block.
-
backward: coalesce consecutive previous blocks staring from the released block.
-
bidi: bidirectional coalesce of consecutive free blocks, moving forward and backward.
EXAMPLE
% allocator -base 1024 -size 2048 -n 5 -c bidi -n 15
configuration:
base: 1024 size: 2048 coalesce: bidi
[1] blocks 2046:1026[-F]
trace:
malloc(1192)
[1] addresses 1026
[2] blocks 1192:1026[-A] 852:2220[PF]
malloc(171)
[2] addresses 1026 2220
[3] blocks 1192:1026[-A] 171:2220[PA] 679:2393[PF]
malloc(800) malloc(800): insufficient memory
malloc(1785) malloc(1785): insufficient memory
malloc(591)
[3] addresses 1026 2220 2393
[4] blocks 1192:1026[-A] 171:2220[PA] 591:2393[PA] 86:2986[PF]
malloc(1275) malloc(1275): insufficient memory
malloc(586) malloc(586): insufficient memory
free(1026)
[2] addresses 2220 2393
[4] blocks 1192:1026[-F] 171:2220[-A] 591:2393[PA] 86:2986[PF]
malloc(1533) malloc(1533): insufficient memory
malloc(265)
[3] addresses 2220 2393 1026
[5] blocks 265:1026[-A] 925:1293[PF] 171:2220[-A] 591:2393[PA] 86:2986[PF]
malloc(920)
[4] addresses 2220 2393 1026 1293
[6] blocks 265:1026[-A] 920:1293[PA] 3:2215[PF] 171:2220[-A] 591:2393[PA] 86:2986[PF]
free(1026)
[3] addresses 2220 2393 1293
[6] blocks 265:1026[-F] 920:1293[-A] 3:2215[PF] 171:2220[-A] 591:2393[PA] 86:2986[PF]
free(2220)
[2] addresses 2393 1293
[5] blocks 265:1026[-F] 920:1293[-A] 176:2215[PF] 591:2393[-A] 86:2986[PF]
free(2393)
[1] addresses 1293
[3] blocks 265:1026[-F] 920:1293[-A] 857:2215[PF]
free(1293)
[0] addresses
[1] blocks 2046:1026[-F]
Documentation
¶
Overview ¶
Allocator simulates memory allocation user library such as malloc(3). It demonstrates basics of managing free memory lists.
SYNOPSIS
allocator [-base num] [-bounds num] [-n num] [-c noop|forward]
EXAMPLE
% allocator/ -base 1024 -size 2048 -n 10 -c forward
configuration:
base: 1024 size: 2048 coalesce: forward
[1] free blocks 2046:1026
trace:
malloc(225)
[1] allocations 1026
[1] free blocks 1819:1253
malloc(326)
[2] allocations 1026 1253
[1] free blocks 1491:1581
free(1026)
[1] allocations 1253
[2] free blocks 225:1026 1491:1581
malloc(1892) malloc(1892): insufficient memory
free(1253)
[0] allocations
[2] free blocks 225:1026 1819:1253
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
internal
|
|
|
heap
Package heap emulates memory allocations, with API simulat to malloc(3).
|
Package heap emulates memory allocations, with API simulat to malloc(3). |
|
report
Package report generates a report for the allocator simulation.
|
Package report generates a report for the allocator simulation. |
|
sim
Package sim simulates client application working with the heap using malloc(3) API: malloc() and free().
|
Package sim simulates client application working with the heap using malloc(3) API: malloc() and free(). |