On Fri, Aug 30, 2013 at 9:55 AM, Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > On Fri, Aug 30, 2013 at 5:54 AM, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: >> On Thu, Aug 29, 2013 at 8:12 PM, Waiman Long <waiman.long@xxxxxx> wrote: >>> On 08/29/2013 07:42 PM, Linus Torvalds wrote: >>>> >>>> Waiman? Mind looking at this and testing? Linus >>> >>> Sure, I will try out the patch tomorrow morning and see how it works out for >>> my test case. >> >> Ok, thanks, please use this slightly updated patch attached here. >> >> It improves on the previous version in actually handling the >> "unlazy_walk()" case with native lockref handling, which means that >> one other not entirely odd case (symlink traversal) avoids the d_lock >> contention. >> >> It also refactored the __d_rcu_to_refcount() to be more readable, and >> adds a big comment about what the heck is going on. The old code was >> clever, but I suspect not very many people could possibly understand >> what it actually did. Plus it used nested spinlocks because it wanted >> to avoid checking the sequence count twice. Which is stupid, since >> nesting locks is how you get really bad contention, and the sequence >> count check is really cheap anyway. Plus the nesting *really* didn't >> work with the whole lockref model. >> >> With this, my stupid thread-lookup thing doesn't show any spinlock >> contention even for the "look up symlink" case. >> >> It also avoids the unnecessary aligned u64 for when we don't actually >> use cmpxchg at all. >> >> It's still one single patch, since I was working on lots of small >> cleanups. I think it's pretty close to done now (assuming your testing >> shows it performs fine - the powerpc numbers are promising, though), >> so I'll split it up into proper chunks rather than random commit >> points. But I'm done for today at least. >> >> NOTE NOTE NOTE! My test coverage really has been pretty pitiful. You >> may hit cases I didn't test. I think it should be *stable*, but maybe >> there's some other d_lock case that your tuned waiting hid, and that >> my "fastpath only for unlocked case" version ends up having problems >> with. >> > > Following this thread with half an eye... Was that "unsigned" stuff > fixed (someone pointed to it). > How do you call that test-patch (subject)? > I would like to test it on my SNB ultrabook with your test-case script. > Can you explain why CONFIG_DEBUG_SPINLOCK=n (here: x86-64)? ( Will this be changed in further releases? ) # CONFIG_DEBUG_SPINLOCK is not set CONFIG_ARCH_USE_CMPXCHG_LOCKREF=y CONFIG_CMPXCHG_LOCKREF=y - Sedat - -- 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
