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

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Date:	Tue, 20 Nov 2012 08:44:45 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
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


* David Rientjes <rientjes@...gle.com> wrote:

> 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.  

Ok - roughly which family/model from /proc/cpuinfo?

> 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?

I'd not expect much sensitivity to RAM size.

> > (A wild guess would be an older 4x Opteron system, 83xx 
> > series or so?)
> 
> Just curious, how you would guess that? [...]

I'm testing numa/core on many systems and the performance 
figures seemed to roughly map to that range.

> [...]  Is there something about Opteron 83xx that make 
> numa/core regress?

Not that I knew of - but apparently there is! I'll try to find a 
system that matches yours as closely as possible and have a 
look.

> > 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!

Yeah, regular perf top output would be very helpful to get a 
general sense of proportion. Thanks!

	Ingo
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