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Message-ID: <CA+icZUVU1u2hMOHT9bVdx=8O5rt9ahBqL=PLZkNpnqo6EXT7Dg@mail.gmail.com> Date: Fri, 30 Aug 2013 12:38:18 +0200 From: Sedat Dilek <sedat.dilek@...il.com> To: Ingo Molnar <mingo@...nel.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Waiman Long <waiman.long@...com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Alexander Viro <viro@...iv.linux.org.uk>, Jeff Layton <jlayton@...hat.com>, Miklos Szeredi <mszeredi@...e.cz>, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, Steven Rostedt <rostedt@...dmis.org>, Andi Kleen <andi@...stfloor.org>, "Chandramouleeswaran, Aswin" <aswin@...com>, "Norton, Scott J" <scott.norton@...com> Subject: Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount On Fri, Aug 30, 2013 at 12:29 PM, Sedat Dilek <sedat.dilek@...il.com> wrote: > On Fri, Aug 30, 2013 at 11:58 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: >> On Fri, Aug 30, 2013 at 11:56 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: >>> On Fri, Aug 30, 2013 at 11:48 AM, Ingo Molnar <mingo@...nel.org> wrote: >>>> >>>> * Sedat Dilek <sedat.dilek@...il.com> wrote: >>>> >>>>> On Fri, Aug 30, 2013 at 9:55 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: >>>>> > On Fri, Aug 30, 2013 at 5:54 AM, Linus Torvalds >>>>> > <torvalds@...ux-foundation.org> wrote: >>>>> >> On Thu, Aug 29, 2013 at 8:12 PM, Waiman Long <waiman.long@...com> 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? >>> >> >> Hmm, I installed linux-tools-common (3.2.0-53.81). >> >> $ perf stat --null --repeat 5 ./t_lockref_from-linus >> perf_3.11.0-rc7 not found >> You may need to install linux-tools-3.11.0-rc7 >> > > [ Sorry for being off-topic ] > > Hey Ingo, > > can you help, please? > > I installed so far all missing -dev packages... > > $ sudo apt-get install libelf-dev libdw-dev libunwind7-dev libslang2-dev > > ...and then want a perf-only build... > > [ See tools/Makefile ] > > $ LANG=C LC_ALL=C make -C tools/ perf_install 2>&1 | tee ../perf_install-log.txt > > This ends up like this: > ... > make[2]: Entering directory > `/home/wearefam/src/linux-kernel/linux/tools/lib/traceevent' > make[2]: Leaving directory > `/home/wearefam/src/linux-kernel/linux/tools/lib/traceevent' > LINK perf > gcc: error: /home/wearefam/src/linux-kernel/linux/tools/lib/lk/liblk.a: > No such file or directory > make[1]: *** [perf] Error 1 > make[1]: Leaving directory `/home/wearefam/src/linux-kernel/linux/tools/perf' > make: *** [perf_install] Error 2 > > $ LANG=C LC_ALL=C ll tools/lib/lk/ > total 20 > drwxr-xr-x 2 wearefam wearefam 4096 Aug 30 12:11 ./ > drwxr-xr-x 4 wearefam wearefam 4096 Jul 11 19:42 ../ > -rw-r--r-- 1 wearefam wearefam 1430 Aug 30 09:56 Makefile > -rw-r--r-- 1 wearefam wearefam 2144 Jul 11 19:42 debugfs.c > -rw-r--r-- 1 wearefam wearefam 619 Jul 11 19:42 debugfs.h > > Why is liblk not built? > > - Sedat - > > P.S.: To clean perf build, run... > > $ LANG=C LC_ALL=C make -C tools/ perf_clean Sorry for flooding... The tools/perf only build seems to be BROKEN in v3.11-rc7. WORKAROUND: $ sudo apt-get install libelf-dev libdw-dev libunwind7-dev libslang2-dev libnuma-dev $ LANG=C LC_ALL=C make -C tools/ liblk $ LANG=C LC_ALL=C make -C tools/ perf_install This works here. - Sedat - -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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