Messages in this thread | | | Date | Thu, 3 Apr 2008 00:12:28 +0200 | From | Andrea Arcangeli <> | Subject | Re: [patch 5/9] Convert anon_vma lock to rw_sem and refcount |
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On Wed, Apr 02, 2008 at 02:56:25PM -0700, Christoph Lameter wrote: > I am a bit surprised that brk performance is that important. There may be
I think it's not brk but fork that is being slowed down, did you oprofile? AIM forks a lot... The write side fast path generating the overscheduling I guess is when the new vmas are created for the child and queued in the parent anon-vma in O(1), so immediate, even preempt-rt would be ok with it spinning and not scheduling, it's just a list_add (much faster than schedule() indeed). Every time there's a collision when multiple child forks simultaneously and they all try to queue in the same anon-vma, things will slowdown.
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