On Wed, 7 May 2008, Ingo Molnar wrote: > > There's far more normal mutex fastpath use during an AIM7 run than any > BKL use. So if it's due to any direct fastpath overhead and the > resulting widening of the window for the real slowdown, we should see a > severe slowdown on AIM7 with CONFIG_MUTEX_DEBUG=y. Agreed? Not agreed. The BKL is special because it is a *single* lock. All the "normal" mutex code use fine-grained locking, so even if you slow down the fast path, that won't cause the same kind of fastpath->slowpath increase. In order to see the fastpath->slowpath thing, you do need to have many threads hitting the same lock: ie the slowdown has to result in real contention. Almost no mutexes have any potential for contention what-so-ever, except for things that very consciously try to hit it (multiple threads doing readdir and/or file creation on the *same* directory etc). The BKL really is special. 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
