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32位的系统中开启物理地址扩展后的内存映射问题
 
 
 
Subject: 32位的系统中开启物理地址扩展后的内存映射问题
Author: harman    Posted: 2007-11-20 17:43    Length: 699 byte(s)
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看ULK的内存寻址这章时碰到这个问题:
32位的系统开启物理地址扩展后能寻址64GB的物理内存,但线性地址并没有增长,也就是说系统有更多的物理内存可供使用,其中有段话:"Clearly, PAE does not enlarge the linear address space of a process, because it deals only with physical addresses. Furthermore, only the kernel can modify the page tables of the processes, thus a process running in User Mode cannot use a physical address space larger than 4 GB. On the other hand, PAE allows the kernel to exploit up to 64 GB of RAM, and thus to increase significantly the number of processes in the system."
它的意思是指用户态的进程不能使用大于4GB的物理内存?也就是说高于4GB的物理内存只能归内核使用?
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Subject: Re: 32位的系统中开启物理地址扩展后的内存映射问题
Author: good02xaut    Posted: 2007-11-20 23:02    Length: 421 byte(s)
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看en内容是这个意思.
单个进程的空间仍然是4G,用户占3G,内核1G.
不过,16个进程的空间就可以是64G的物理内存啦.内核可以提供相应的page table.
这和没有PAE还是有很大区别的

进程1可能分配0-3G物理内存
进程2可能分配6-9G物理内存.

单个进程在32bit系统中,不能寻址(虚拟地址)超过4G.
PAE可以是多个进程使用超过4G的物理内存,通过内核的扩展功能

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Subject: Re: 32位的系统中开启物理地址扩展后的内存映射问题
Author: harman    Posted: 2007-11-21 08:46    Length: 56 byte(s)
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哦 知道了文中使用的是 larger than 我理解为higher than了
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