On Wed, 7 May 2008, Ingo Molnar wrote: > > another idea: my trial-baloon patch should test your theory too, because > the generic down_trylock() is still the 'fat' version, it does: I agree that your trial-balloon should likely get rid of the big regression, since it avoids the scheduler. So with your patch, lock_kernel() ends up being just a rather expensive spinlock. And yes, I'd expect that it should get rid of the 40% cost, because while it makes lock_kernel() more expensive than a spinlock and you might end up having a few more cacheline bounces on the lock due to that, that's still the "small" expense compared to going through the whole scheduler on conflicts. So I'd expect that realistically the performance difference between your version and just plain spinlocks shouldn't be *that* big. I'd expect it to be visible, but in the (low) single-digit percentage range rather than in any 40% range. That's just a guess. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
