Linux 3.19-rc3

Andreas Mohr andi at
Sat Jan 10 02:46:27 PST 2015

Linus Torvalds wrote:
> I dunno. I do know that you definitely don't want to haev a
> desktop/workstation with 64kB pages.

Yet that is what any VirtualAlloc() call on Windows does
(well, not exactly *page* granularity but *allocation* granularity there).
Prime example: do a naively specific/custom VirtualAlloc() request
for a simple string Hello World\0 allocation (11+1 bytes),
get one page (4kB, "Private Data") plus "overhead" (60kB, "Unusable").
--> allocation efficiency: 0.01831%(!).
And that does hurt plenty IME, especially on a 32bit address space's
very limited 2GB/3GB total per Win32 process.
"Why is address space allocation granularity 64K?"

One thing less left to wonder why 'doze is such a performance pig...

Andreas Mohr

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