Cc: Ulrich Drepper <drepper@...>, Arjan van de Ven <arjan@...>, <akpm@...>, <hugh@...>, <linux-mm@...>, <linux-kernel@...>, <briangrant@...>, <cgd@...>, <mbligh@...>, Linus Torvalds <torvalds@...>, Thomas Gleixner <tglx@...>, H. Peter Anvin <hpa@...>
Of course - what you are missing is that _10 milliseconds_ thread
creation overhead is completely unacceptable overhead: it is so bad as
if we didnt even support it.
Nonsense, i had such a P4 based 64-bit box and it was painful. Everyone
with half a brain used them as 32-bit machines. Nor is the
context-switch overhead in any way significant. Plus, as Arjan mentioned
it, only the earliest P4 64-bit CPUs had this problem.
that's a lot of handwaving with no actual numbers. The numbers in this
discussion show that the context-switch overhead is small and that the
overhead on perfectly good systems that hit this limit is obscurely
high.
I'd love to zap MAP_32BIT this very minute from the kernel, but you
originally shaped the whole thing in such a stupid way that makes its
elimination impossible now due to ABI constraints. It would have cost
you _nothing_ to have added MAP_64BIT_STACK back then, but the quick &
sloppy solution was to reuse MAP_32BIT for 64-bit tasks. And you are
stupid about it even now. Bleh.
The correct solution is to eliminate this flag from glibc right now, and
maybe add the MAP_64BIT_STACK flag as well, as i posted it - if anyone
with such old boxes still cares (i doubt anyone does). That flag then
will take its usual slow route. Ulrich?
Ingo
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