Andi Kleen a écrit :
Kirill Korotaev <[email protected]> writes:
Please help with a not simple question about spin_lock/spin_unlock on
SMP archs. The question is whether concurrent spin_lock()'s should
acquire it in more or less "fair" fashinon or one of CPUs can starve
any arbitrary time while others do reacquire it in a loop.
They are not fully fair because of the NUMAness of the system.
Same on many other NUMA systems.
We considered long ago to use queued locks to avoid this, but
they are quite costly for the uncongested case and never seemed worth it.
So live with it.
Unrelated, but that reminds me that current spinlock implementation on x86
imply that NR_CPUS should be < 128.
Maybe we should reflect this in Kconfig ?
config NR_CPUS
range 2 128
Or use a plain int for spinlock, instead of a signed char.
Eric
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