On Wed, 7 Jan 2009, Gregory Haskins wrote: > > Can I ask a simple question in light of all this discussion? > > "Is get_task_struct() really that bad?" Yes. It's an atomic access (two, in fact, since you need to release it too), which is a huge deal if we're talking about a timing-critical section of code. And this is timing-critical, or we wouldn't even care - even in the contention case. Admittedly btrfs apparently makes it more so that it _should_ be, but Peter had some timings that happened with just regular create/unlink that showed a big difference. So the whole and only point of spinning mutexes is to get rid of the scheduler overhead, but to also not replace it with some other thing ;) Linus -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
