[lkml]   [2007]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [patch 1/4] x86: FIFO ticket spinlocks
    Nick Piggin wrote:
    > Introduce ticket lock spinlocks for x86 which are FIFO. The implementation
    > is described in the comments. The straight-line lock/unlock instruction
    > sequence is slightly slower than the dec based locks on modern x86 CPUs,
    > however the difference is quite small on Core2 and Opteron when working out of
    > cache, and becomes almost insignificant even on P4 when the lock misses cache.
    > trylock is more significantly slower, but they are relatively rare.
    > On an 8 core (2 socket) Opteron, spinlock unfairness is extremely noticable,
    > with a userspace test having a difference of up to 2x runtime per thread, and
    > some threads are starved or "unfairly" granted the lock up to 1 000 000 (!)
    > times. After this patch, all threads appear to finish at exactly the same
    > time.

    I had observed this phenomenon on some 8-ways here as well, but I didn't
    have the bandwidth to code something up. Thumbs up!

    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2007-11-01 15:43    [from the cache]
    ©2003-2014 Jasper Spaans. hosted at Digital Ocean