Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756030Ab3H3K3i (ORCPT ); Fri, 30 Aug 2013 06:29:38 -0400 Received: from mail-wi0-f173.google.com ([209.85.212.173]:51112 "EHLO mail-wi0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754311Ab3H3K3g (ORCPT ); Fri, 30 Aug 2013 06:29:36 -0400 MIME-Version: 1.0 Reply-To: sedat.dilek@gmail.com In-Reply-To: References: <1377751465.4028.20.camel@pasglop> <20130829070012.GC27322@gmail.com> <52200DAE.2020303@hp.com> <20130830094857.GA14502@gmail.com> Date: Fri, 30 Aug 2013 12:29:34 +0200 Message-ID: Subject: Re: [PATCH v7 1/4] spinlock: A new lockref structure for lockless update of refcount From: Sedat Dilek To: Ingo Molnar Cc: Linus Torvalds , Waiman Long , Benjamin Herrenschmidt , Alexander Viro , Jeff Layton , Miklos Szeredi , Ingo Molnar , Thomas Gleixner , linux-fsdevel , Linux Kernel Mailing List , Peter Zijlstra , Steven Rostedt , Andi Kleen , "Chandramouleeswaran, Aswin" , "Norton, Scott J" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5662 Lines: 148 On Fri, Aug 30, 2013 at 11:58 AM, Sedat Dilek wrote: > On Fri, Aug 30, 2013 at 11:56 AM, Sedat Dilek wrote: >> On Fri, Aug 30, 2013 at 11:48 AM, Ingo Molnar wrote: >>> >>> * Sedat Dilek wrote: >>> >>>> On Fri, Aug 30, 2013 at 9:55 AM, Sedat Dilek wrote: >>>> > On Fri, Aug 30, 2013 at 5:54 AM, Linus Torvalds >>>> > wrote: >>>> >> On Thu, Aug 29, 2013 at 8:12 PM, Waiman Long 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/