内核知识点收集
7. x86_64地址空间分配
Virtual memory map with 4 level page tables:
0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
hole caused by [48:63] sign extension
ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor
ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
... unused hole ...
ffffec0000000000 - fffffc0000000000 (=44 bits) kasan shadow memory (16TB)
... unused hole ...
ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
... unused hole ...
ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0
ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
The direct mapping covers all memory in the system up to the highest
memory address (this means in some cases it can also include PCI memory
holes).
vmalloc space is lazily synchronized into the different PML4 pages of
the processes using the page fault handler, with init_level4_pgt as
reference.
Current X86-64 implementations only support 40 bits of address space,
but we support up to 46 bits. This expands into MBZ space in the page tables.
->trampoline_pgd:
We map EFI runtime services in the aforementioned PGD in the virtual
range of 64Gb (arbitrarily set, can be raised if needed)
0xffffffef00000000 - 0xffffffff00000000
8. x86_64地址映射模型
9. linux进程记录内存映射关系
10. 物理内存相关概念
a. 节点(node)
非均匀性内存。CPU对不同的内存单元的访问时间不一样，访问时间相同的的一块内存称为一个节点(node)
b. 区域(zone)
每一个节点又进一步分为许多块，称为区域(zone)。区域表示一块内存区中的范围。
ZONE_DMA 内存开始的16MB
ZONE_NORMAL 16MB-896MB
ZONE_HIGHMEM 896MB-结束
c. 页面(page)
...
11. 空闲内存管理
12. 内存分配回收接口
kmalloc()/vmalloc()/__get_free_pages()/alloc_pages()
kfree()/vfree()/free_pages()
13. 内核进程栈
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