The standard futex mechanism in the Linux kernel uses a global hash to store
transient state. Collisions on that hash can lead to performance degradation
and on real-time enabled kernels to unbound priority inversions.
To guarantee futexes without collisions on the global kernel hash, we provide
a mechanism to attach to a futex. This creates futex private state which
avoids hash collisions and on NUMA systems also cross node memory accesses.
The full explanation of the mechanism is in the changelog of
patch 4/7 'futex: Add support for attached futexes'.
The last two patches in the series contain a first update to the futex man
page and initial glibc support.
For your conveniance the kernel part is available at:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git WIP.futex
Thanks,
tglx
