From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>,
Linux-Next Mailing List <linux-next@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: manual merge of the akpm tree with the tip tree
Date: Fri, 31 Mar 2017 19:48:18 +0200 [thread overview]
Message-ID: <20170331174818.6sqwonjhuonjmpif@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170331160242.GF4543@tassilo.jf.intel.com>
On Fri, Mar 31, 2017 at 09:02:42AM -0700, Andi Kleen wrote:
> On Fri, Mar 31, 2017 at 04:45:46PM +0200, Peter Zijlstra wrote:
> > On Fri, Mar 31, 2017 at 06:54:48AM -0700, Andi Kleen wrote:
> > > > Argh!
> > > >
> > > > Andrew, please drop that patch. And the x86 out-of-line of __atomic_add_unless().
> > >
> > > Why dropping the second? Do you have something better?
> >
> > The try_cmpxchg() patches save about half the text, and do not have the
> > out-of-line penalty as shown here:
> >
> > https://lkml.kernel.org/r/20170322165144.dtidvvbxey7w5pbd@hirez.programming.kicks-ass.net
>
> Where is the source for the benchmark?
In that email; heck marc.info even provides a downloadable link, you
don't even have to go find it in your local lkml archives.
> Based on the description it sounds like it's testing atomic_inc(),
> which my patches don't change.
Yes, reading is hard.
It tests:
lock incl
vs
call refcount_inc
vs
$inlined refcount_inc
And refcount_inc() is more complex than add_unless().
> BTW testing such things in tight loops is bad practice. If you run
> them back to back the CPU pipeline has to do much more serialization,
> which is usually not realistic and drastically overestimates
> the overhead.
>
> A better practice is to run some real workload. If you want to see
> cycle counts you can look at LBR cycles, or PT cycles from sampling or tracing.
Hey, at least I did benchmark it. You just waved your hands and are
causing extra work for other people.
> > > On the first there were no 0day regressions, so at least basic performance
> > > checking has been done.
> >
> > The first is superseded by much better patches in the scheduler tree.
>
> Which patches exactly? The new patches shrink the text too?
Try your local google foo; or look at the patch that conflicted, its
that one and the next.
In the end it comes down to -mm carrying patches against trees that are
maintained elsewhere without acks from said maintainers. I don't feel
bad about causing conflicts.
next prev parent reply other threads:[~2017-03-31 17:48 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-31 5:44 linux-next: manual merge of the akpm tree with the tip tree Stephen Rothwell
2017-03-31 6:42 ` Peter Zijlstra
2017-03-31 13:54 ` Andi Kleen
2017-03-31 14:45 ` Peter Zijlstra
2017-03-31 16:02 ` Andi Kleen
2017-03-31 17:48 ` Peter Zijlstra [this message]
-- strict thread matches above, loose matches on Subject: below --
2020-05-29 10:57 Stephen Rothwell
2020-05-29 10:49 Stephen Rothwell
2020-01-22 6:37 Stephen Rothwell
2019-02-13 6:49 Stephen Rothwell
2019-02-13 19:59 ` Andrew Morton
2018-01-09 5:02 Stephen Rothwell
2018-01-09 10:36 ` Andy Shevchenko
2017-10-16 18:48 Mark Brown
2017-10-16 20:01 ` Mark Brown
2017-04-12 7:08 Stephen Rothwell
2017-03-24 5:40 Stephen Rothwell
2017-03-24 8:05 ` Peter Zijlstra
2016-03-10 5:28 Stephen Rothwell
2016-03-10 8:00 ` Ingo Molnar
2016-03-10 20:38 ` Andrew Morton
2016-02-09 4:50 Stephen Rothwell
2016-02-09 14:04 ` Matt Fleming
2016-02-09 14:07 ` Ingo Molnar
2015-06-09 14:12 Stephen Rothwell
2015-04-08 8:49 Stephen Rothwell
2015-04-08 15:13 ` Ingo Molnar
2015-04-08 20:46 ` Andrew Morton
2015-04-08 21:57 ` Stephen Rothwell
2014-03-21 6:45 Stephen Rothwell
2014-01-13 6:17 Stephen Rothwell
2013-04-23 7:17 Stephen Rothwell
2013-02-14 4:33 Stephen Rothwell
2013-02-14 4:25 Stephen Rothwell
2013-02-14 4:34 ` H. Peter Anvin
2013-02-04 7:00 Stephen Rothwell
2013-01-28 12:29 Stephen Rothwell
2012-12-10 8:29 Stephen Rothwell
2012-12-10 10:46 ` Ingo Molnar
2012-12-10 8:25 Stephen Rothwell
2012-12-10 8:20 Stephen Rothwell
2012-12-10 8:11 Stephen Rothwell
2012-12-10 8:01 Stephen Rothwell
2012-12-10 11:13 ` Will Deacon
2012-12-10 7:47 Stephen Rothwell
2012-11-15 6:32 Stephen Rothwell
2012-10-01 14:22 Stephen Rothwell
2012-09-27 7:15 Stephen Rothwell
2012-09-27 7:10 Stephen Rothwell
2012-09-27 7:04 Stephen Rothwell
2012-09-27 6:57 Stephen Rothwell
2012-09-27 6:49 Stephen Rothwell
2012-07-27 3:50 Stephen Rothwell
2012-07-25 4:08 Stephen Rothwell
2012-07-25 7:10 ` Ingo Molnar
2012-07-25 7:35 ` Johannes Weiner
2012-07-25 18:57 ` Andrew Morton
2012-07-25 19:03 ` Ingo Molnar
2012-07-25 19:26 ` Andrew Morton
2012-07-26 7:51 ` Ingo Molnar
2012-07-26 18:05 ` Andrew Morton
2012-07-25 19:20 ` Johannes Weiner
2012-07-26 7:03 ` Stephen Rothwell
2012-05-21 8:29 Stephen Rothwell
2012-05-21 8:04 Stephen Rothwell
2012-05-21 7:59 Stephen Rothwell
2012-03-27 4:57 Stephen Rothwell
2012-03-26 4:01 Stephen Rothwell
2012-03-26 5:20 ` Alex Shi
2012-03-08 6:32 Stephen Rothwell
2012-03-08 6:28 Stephen Rothwell
2012-02-29 6:27 Stephen Rothwell
2012-02-28 4:52 Stephen Rothwell
2012-02-27 5:53 Stephen Rothwell
2012-02-27 5:57 ` Cyrill Gorcunov
2012-02-27 6:02 ` H. Peter Anvin
2012-02-27 6:05 ` Cyrill Gorcunov
2012-02-27 6:01 ` H. Peter Anvin
2012-02-27 6:19 ` Stephen Rothwell
2012-02-27 5:44 Stephen Rothwell
2012-02-27 5:33 Stephen Rothwell
2012-02-27 5:23 Stephen Rothwell
2012-02-27 5:16 Stephen Rothwell
2011-12-06 4:04 Stephen Rothwell
2011-09-27 7:13 Stephen Rothwell
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