On Wed, 2009-01-07 at 09:50 -0800, Linus Torvalds wrote: > > On Wed, 7 Jan 2009, Chris Mason wrote: > > > > So far I haven't found any btrfs benchmarks where this is slower than > > mutexes without any spinning. But, it isn't quite as fast as the btrfs > > spin. > > Quite frankly, from our history with ext3 and other filesystems, using a > mutex in the filesystem is generally the wrong thing to do anyway. > > Are you sure you can't just use a spinlock, and just release it over IO? > The "have to do IO or extend the btree" case is usually pretty damn clear. > > Because it really sounds like you're lock-limited, and you should just try > to clean it up. A pure "just spinlock" in the hotpath is always going to > be better. There are definitely ways I can improve performance for contention in the hot btree nodes, and I think it would be a mistake to tune the generic adaptive locks just for my current code. But, it isn't a bad test case to compare the spin with the new patch and with the plain mutex. If the adaptive code gets in, I think it would be best for me to drop the spin. Either way there's more work to be done in the btrfs locking code. -chris -- 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
