linux-kernel - Re: [PATCH 00/27] Latest numa/core release, v16

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Message-ID: <alpine.DEB.2.00.1211192213420.5498@chino.kir.corp.google.com>
Date:	Mon, 19 Nov 2012 22:20:39 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Ingo Molnar <mingo@...nel.org>
cc:	Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Christoph Lameter <cl@...ux.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 00/27] Latest numa/core release, v16

On Tue, 20 Nov 2012, Ingo Molnar wrote:

> > > numa/core at ec05a2311c35 ("Merge branch 'sched/urgent' into 
> > > sched/core") had an average throughput of 136918.34 
> > > SPECjbb2005 bops, which is a 6.3% regression.
> > 
> > perftop during the run on numa/core at 01aa90068b12 ("sched: 
> > Use the best-buddy 'ideal cpu' in balancing decisions"):
> > 
> >     15.99%  [kernel]  [k] page_fault                         
> >      4.05%  [kernel]  [k] getnstimeofday                     
> >      3.96%  [kernel]  [k] _raw_spin_lock                     
> >      3.20%  [kernel]  [k] rcu_check_callbacks                
> >      2.93%  [kernel]  [k] generic_smp_call_function_interrupt
> >      2.90%  [kernel]  [k] __do_page_fault                    
> >      2.82%  [kernel]  [k] ktime_get                          
> 
> Thanks for testing, that's very interesting - could you tell me 
> more about exactly what kind of hardware this is? I'll try to 
> find a similar system and reproduce the performance regression.
> 

This happened to be an Opteron (but not 83xx series), 2.4Ghz.  Your 
benchmarks were different in the number of cores but also in the amount of 
memory, do you think numa/core would regress because this is 32GB and not 
64GB?

> (A wild guess would be an older 4x Opteron system, 83xx series 
> or so?)
> 

Just curious, how you would guess that?  Is there something about Opteron 
83xx that make numa/core regress?

> Also, the profile looks weird to me. Here is how perf top looks 
> like on my system during a similarly configured, "healthy" 
> SPECjbb run:
> 
>  91.29%  perf-6687.map            [.] 0x00007fffed1e8f21
>   4.81%  libjvm.so                [.] 0x00000000007004a0
>   0.93%  [vdso]                   [.] 0x00007ffff7ffe60c
>   0.72%  [kernel]                 [k] do_raw_spin_lock
>   0.36%  [kernel]                 [k] generic_smp_call_function_interrupt
>   0.10%  [kernel]                 [k] format_decode
>   0.07%  [kernel]                 [k] rcu_check_callbacks
>   0.07%  [kernel]                 [k] apic_timer_interrupt
>   0.07%  [kernel]                 [k] call_function_interrupt
>   0.06%  libc-2.15.so             [.] __strcmp_sse42
>   0.06%  [kernel]                 [k] irqtime_account_irq
>   0.06%  perf                     [.] 0x000000000004bb7c
>   0.05%  [kernel]                 [k] x86_pmu_disable_all
>   0.04%  libc-2.15.so             [.] __memcpy_ssse3
>   0.04%  [kernel]                 [k] ktime_get
>   0.04%  [kernel]                 [k] account_group_user_time
>   0.03%  [kernel]                 [k] vbin_printf
> 
> and that is what SPECjbb does: it spends 97% of its time in Java 
> code - yet there's no Java overhead visible in your profile - 
> how is that possible? Could you try a newer perf on that box:
> 

It's perf top -U, the benchmark itself was unchanged so I didn't think it 
was interesting to gather the user symbols.  If that would be helpful, let 
me know!
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