Why does TASK_UNMAPPED_BASE=TASK_SIZE/3 ?

Steve Willer (willer@interlog.com)
Mon, 14 Jun 1999 18:58:45 -0400 (EDT)

I've been doing a little kernel source browsing (and ld.so source
browsing) towards the goal of someday being able to shmat() a very large
shared memory block (like, say, 1.5GB on a 2GB machine). This is important
for fair-sized DB's.

So, what I'm wondering is: Why is the default start location for mmap()'s
one third up the task size? The way things currently are, shared library
loading gets in the way of large contiguous allocations on
virtual-space-starved arches like ia32. Why not put the mmap() as low as
possible?

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