On Fri, 4 Aug 2000, Matthew Dillon wrote:

:You have to have some page table locking mechanism for SMP eventually: I
:think you miss some of the problems because the current FreeBSD SMP stuff
:is mostly still "big kernel lock" (outdated info?), and you'll end up
:kicking yourself in a big way when you have the 300 processes sharing the
:same lock for that region..

    If it were a long-held lock I'd worry, but if it's a lock on a pte
    I don't think it can hurt.  After all, even with separate page tables
    if 300 processes fault on the same backing file offset you are going
    to hit a bottleneck with MP locking anyway, just at a deeper level
    (the filesystem rather then the VM system).

Erm... I'm not sure about that - for one thing, you are not caching
results of bmap(). We do. And our VFS is BKL-free, so contention really
hits only on the VOP_BALLOC() level (that can be fixed too, but that's
another story).

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