On Fri, 03 Jan 2014 10:01:47 -0800 Dave Hansen <d...@sr71.net> wrote:
> This is a minor update from the last version. The most notable > thing is that I was able to demonstrate that maintaining the > cmpxchg16 optimization has _some_ value. > > Otherwise, the code changes are just a few minor cleanups. > > --- > > SLUB depends on a 16-byte cmpxchg for an optimization which > allows it to not disable interrupts in its fast path. This > optimization has some small but measurable benefits: > > http://lkml.kernel.org/r/52b345a3.6090...@sr71.net So really the only significant benefit from the cmpxchg16 is with cache-cold eight-byte kmalloc/kfree? 8% faster in this case? But with cache-hot kmalloc/kfree the benefit of cmpxchg16 is precisely zero. This is really weird and makes me suspect a measurement glitch. Even if this 8% is real, it's unclear that it's worth all the complexity the cmpxchg16 adds. It would be really useful (hint :)) if we were to know exactly where that 8% is coming from - perhaps it's something which is not directly related to the cmpxchg16, and we can fix it separately. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
