Messages in this thread | | | Date | Tue, 22 Jul 2014 10:39:17 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH 0/5] futex: introduce an optimistic spinning futex |
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On Tue, 22 Jul 2014, Peter Zijlstra wrote: > Anyway, there is one big fail in the entire futex stack that we 'need' > to sort some day and that is NUMA. Some people (again database people) > explicitly do not use futexes and instead use sysvsem because of this. > > The problem with numa futexes is that because they're vaddr based there > is no (persistent) node information. You always end up having to fall > back to looking in all nodes before you can guarantee there is no > matching futex. > > One way to achieve it is by extending the futex value to include a node > number, but that's obviously a complete ABI break. Then again, it should > be pretty straight fwd, since the node number doesn't need to be part of > the actual atomic update part, just part of the userspace storage.
So you want per node hash buckets, right? Fair enough, but how do you make sure, that no thread/process on a different node is fiddling with that "node bound" futex as well?
Thanks,
tglx
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