[kernelreadfans] ZONE NORMAL size？
- From: "oyk" <oyk@xxxxxxxxxxx>
- To: kernelreadfans <kernelreadfans@xxxxxxxxxxxxx>
- Date: Fri, 6 Jun 2003 18:4:40 +0800
Hi，
对于Understanding VM的5.1节最后一段话
The region required for vmalloc(), kmap() and the fixed virtual address
mapping is what limits the size of ZONE_NORMAL. As
the running kernel needs these functions, a region of at least VMALLOC_RESERVE
will be reserved at the top of the address
space. VMALLOC_RESERVE is architecture specific but on the x86, it is defined
as 128MiB. This is why ZONE_NORMAL is
generally referred to being only 896MiB in size; it is the 1GiB of the upper
potion of the linear address space minus the
minimum 128MiB that is reserved for the vmalloc region.
我还是没有理解为什么ZONE_NORMAL最大是896M。
而图5-1指出的VMALLOC_START－VMALLOC_END区域只能用于vmalloc？
从PKMAP_BASE开始，只能用于kmap？
VMALLOC_RESERVE表示什么，如果内存不够896M，VMALLOC_RESERVE还有意义吗？
Best Regards
Ouyang Kai
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