Jörn Engel wrote:
On Sun, 7 December 2008 23:32:32 +0000, Phillip Lougher wrote:
Currently, as mentioned above, Squashfs decompresses into a single
contiguous output buffer. But, due to the linux kernel mailing list's
dislike of vmalloc, this is being changed.
Don't blame lkml, blame Intel and IBM. Back in the days of the 386, a
beefy machine had 8MB of physical memory and 4GB of virtual memory
space. Noone had to worry about fragmentation anymore. If you needed a
1MB buffer, you'd just round up some 256 pages and instruct the mmu to
map them into a large contiguous address range in the virtual address
space. Life was good indeed.
But physical memory has constantly grown since, while the virtual memory
space has for a long time stagnated. Intel even introduced some
hardware hacks to use up to 64GB of physical memory with a measly 4GB of
virtual memory. Now it was _virtual_ memory fragmentation that you had
to worry about.
These days most CPUs you'd buy are 64bit, so virtual memory space has
become useful again. But as a kernel hacker, you have little control
over what hardware everyone is using. And those weird systems with
more physical than virtual memory are still around. :(
Jörn
Yes, I'm aware of the issues with vmalloc on older hardware.
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