On Fri, Aug 30, 2013 at 11:48 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > * Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > >> 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. >> > >> >> Here on Ubuntu/precise v12.04.3 AMD64 I get these numbers for total loops: >> >> lockref: w/o patch | w/ patch >> ====================== >> Run #1: 2.688.094 | 2.643.004 >> Run #2: 2.678.884 | 2.652.787 >> Run #3: 2.686.450 | 2.650.142 >> Run #4: 2.688.435 | 2.648.409 >> Run #5: 2.693.770 | 2.651.514 >> >> Average: 2687126,6 VS. 2649171,2 ( ???37955,4 ) > > For precise stddev numbers you can run it like this: > > perf stat --null --repeat 5 ./test > > and it will measure time only and print the stddev in percentage: > > Performance counter stats for './test' (5 runs): > > 1.001008928 seconds time elapsed ( +- 0.00% ) > Hi Ingo, that sounds really good :-). AFAICS 'make deb-pkg' does not have support to build linux-tools Debian package where perf is included. Can I run an older version of perf or should I / have to try with the one shipped in Linux v3.11-rc7+ sources? How can I build perf standalone, out of my sources? - 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
