Linux - 内存 - 预留内存占用分析

说明

• Linux启动log中会显示平台的内存信息，公司SOC平台，物理DRAM实际size是128M，但是启动log中total size不足128MB，并且预留内存（82272K reserved）过多，启动log如下：

Memory: 48032K/130304K available (3478K kernel code, 500K rwdata, 1504K rodata, 124K init, 212K bss, 82272K reserved, 0K cma-reserved)

• total size：130304K，预留size 82272K相减得到剩余size（48032K）。

分析

• 平台使用memblock管理早期内存分配，打开memblock debug重启后，启动log如下：

memblock_reserve: [0x0000000080200000-0x00000000807bdfff] setup_bootmem+0x86/0x162
memblock_reserve: [0x0000000082dcd000-0x0000000082dd2fff] setup_bootmem+0xde/0x162
memblock_reserve: [0x0000000080000000-0x000000008007ffff] setup_bootmem+0x100/0x162
memblock_reserve: [0x0000000080000000-0x000000008007ffff] early_init_fdt_scan_reserved_mem+0x46/0x76
memblock_reserve: [0x0000000080000000-0x000000008003ffff] __fdt_scan_reserved_mem+0x20a/0x27a
memblock_reserve: [0x000000008377e000-0x000000008393ffff] fdt_init_reserved_mem+0x306/0x42a
memblock_reserve: [0x0000000083940000-0x0000000087f3ffff] fdt_init_reserved_mem+0x360/0x42a
Ion: Ion memory setup at 0x0000000083940000 size 70 MiB
OF: reserved mem: initialized node ion, compatible id ion-region
MEMBLOCK configuration:
 memory size = 0x0000000007f40000 reserved size = 0x0000000004e06000
 memory.cnt  = 0x1
 memory[0x0]	[0x0000000080000000-0x0000000087f3ffff], 0x0000000007f40000 bytes flags: 0x0
 reserved.cnt  = 0x4
 reserved[0x0]	[0x0000000080000000-0x000000008007ffff], 0x0000000000080000 bytes flags: 0x0
 reserved[0x1]	[0x0000000080200000-0x00000000807bdfff], 0x00000000005be000 bytes flags: 0x0
 reserved[0x2]	[0x0000000082dcd000-0x0000000082dd2fff], 0x0000000000006000 bytes flags: 0x0
 reserved[0x3]	[0x000000008377e000-0x0000000087f3ffff], 0x00000000047c2000 bytes flags: 0x0
memblock_reserve: [0x000000008377d000-0x000000008377dfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008377c000-0x000000008377cfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008377b000-0x000000008377bfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008377a000-0x000000008377afff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083779000-0x0000000083779fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083778000-0x0000000083778fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083777000-0x0000000083777fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083776000-0x0000000083776fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083775000-0x0000000083775fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083774000-0x0000000083774fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083773000-0x0000000083773fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083772000-0x0000000083772fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083771000-0x0000000083771fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083770000-0x0000000083770fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376f000-0x000000008376ffff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376e000-0x000000008376efff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376d000-0x000000008376dfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376c000-0x000000008376cfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376b000-0x000000008376bfff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x000000008376a000-0x000000008376afff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083769000-0x0000000083769fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083768000-0x0000000083768fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083767000-0x0000000083767fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083766000-0x0000000083766fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083765000-0x0000000083765fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083764000-0x0000000083764fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083763000-0x0000000083763fff] memblock_alloc_range_nid+0x96/0xc2
memblock_reserve: [0x0000000083762000-0x0000000083762fff] memblock_alloc_range_nid+0x96/0xc2
memblock