Peter Teoh 写道:
On Nov 13, 2007 8:58 PM, Jacky(GuangXiang Lee) <gxli@xxxxxxxxxxx> wrote:
hi ,
what is "flat" memory and "sparse" memory, and their difference?
thanks.
Sorry, I did not read the source code, neither any paper/article on
this feature yet for lack of time...just purely my guess:
Normally sparse filesystem means that not every bytes need to have a
physical storage available, so to store a 2TB sparse file, u may
theoretically just need 1KB file, if the content of the 2TB sparse
just access max 1KB of data, but u will need some metadata to map the
data to its exact location within the 2TB storage space.
Similarly for memory - if u maintain many different pagetable for CR3
mapping, it is possible to setup the CPU to map to a large memory,
given that the physical memory is only much smaller. Contrast this
to uniform flat virtual memory - whereby ONE pagetable is use to map
the memory, and so every bytes that theoretically can be accessed have
to have a physical byte to account for.
Oh, well guess. With linux kernel, the physical memory is managed
initially by "sparse mode", which divides all avalable memory into
"sections".Each section contain typically 128M Bytes.So as to deal with
the probable holes in the entire physical memory map.
Is there any article/paper found about this?
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