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Date: Tue, 20 Nov 2012 10:06:37 +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:
>
> > > This happened to be an Opteron (but not 83xx series), 2.4Ghz.
> >
> > Ok - roughly which family/model from /proc/cpuinfo?
>
> It's close enough, it's 23xx.
Ok - which family/model number in /proc/cpuinfo?
I'm asking because that will matter most to page fault
micro-characteristics and the 23xx series existed in Barcelona
form as well (family/model of 16/2) and it still exists in its
current Shanghai form as well.
My guess is Barcelona 16/2?
If that is correct then the closest I can get to your topology
is a 4-socket 32-way Opteron system with 32 GB of RAM - which
seems close enough for testing purposes.
But checking numa/core on such a system still keeps me
absolutely puzzled, as I get the following with a similar
16-warehouses SPECjbb 2005 test, using java -Xms8192m -Xmx8192m
-Xss256k sizing, THP enabled, 2x 240 seconds runs (I tried to
configure it all very close to yours), using -tip-a07005cbd847:
kernel warehouses transactions/sec
--------- ----------
v3.7-rc6: 16 197802
16 197997
numa/core: 16 203086
16 203967
So sadly numa/core is about 2%-3% faster on this 4x4 system too!
:-/
But I have to say, your SPECjbb score is uncharacteristically
low even for an oddball-topology Barcelona system - which is the
oldest/slowest system I can think of. So there might be more to
this.
To further characterise a "good" SPECjbb run, there's no
page_fault overhead visible in perf top:
Mainline profile:
94.99% perf-1244.map [.] 0x00007f04cd1aa523
2.52% libjvm.so [.] 0x00000000007004a1
0.62% [vdso] [.] 0x0000000000000972
0.31% [kernel] [k] clear_page_c
0.17% [kernel] [k] timekeeping_get_ns.constprop.7
0.11% [kernel] [k] rep_nop
0.09% [kernel] [k] ktime_get
0.08% [kernel] [k] get_cycles
0.06% [kernel] [k] read_tsc
0.05% libc-2.15.so [.] __strcmp_sse2
numa/core profile:
95.66% perf-1201.map [.] 0x00007fe4ad1c8fc7
1.70% libjvm.so [.] 0x0000000000381581
0.59% [vdso] [.] 0x0000000000000607
0.19% [kernel] [k] do_raw_spin_lock
0.11% [kernel] [k] generic_smp_call_function_interrupt
0.11% [kernel] [k] timekeeping_get_ns.constprop.7
0.08% [kernel] [k] ktime_get
0.06% [kernel] [k] get_cycles
0.05% [kernel] [k] __native_flush_tlb
0.05% [kernel] [k] rep_nop
0.04% perf [.] add_hist_entry.isra.9
0.04% [kernel] [k] rcu_check_callbacks
0.04% [kernel] [k] ktime_get_update_offsets
0.04% libc-2.15.so [.] __strcmp_sse2
No page fault overhead (see the page fault rate further below) -
the NUMA scanning overhead shows up only through some mild TLB
flush activity (which I'll fix btw).
[ Stupid question: cpufreq is configured to always-2.4GHz,
right? If you could send me your kernel config (you can do
that privately as well) then I can try to boot it and see. ]
> > > 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!
>
> Ok, here it is:
>
> 91.24% perf-10971.map [.] 0x00007f116a6c6fb8
> 1.19% libjvm.so [.] instanceKlass::oop_push_contents(PSPromotionMa
> 1.04% libjvm.so [.] PSPromotionManager::drain_stacks_depth(bool)
> 0.79% libjvm.so [.] PSPromotionManager::copy_to_survivor_space(oop
> 0.60% libjvm.so [.] PSPromotionManager::claim_or_forward_internal_
> 0.58% [kernel] [k] page_fault
> 0.28% libc-2.3.6.so [.] __gettimeofday
> 0.26% libjvm.so [.] Copy::pd_disjoint_words(HeapWord*, HeapWord*, unsigned
> 0.22% [kernel] [k] getnstimeofday
> 0.18% libjvm.so [.] CardTableExtension::scavenge_contents_parallel(ObjectS
> 0.15% [kernel] [k] _raw_spin_lock
> 0.12% [kernel] [k] ktime_get_update_offsets
> 0.11% [kernel] [k] ktime_get
> 0.11% [kernel] [k] rcu_check_callbacks
> 0.10% [kernel] [k] generic_smp_call_function_interrupt
> 0.10% [kernel] [k] read_tsc
> 0.10% [kernel] [k] clear_page_c
> 0.10% [kernel] [k] __do_page_fault
> 0.08% [kernel] [k] handle_mm_fault
> 0.08% libjvm.so [.] os::javaTimeMillis()
> 0.08% [kernel] [k] emulate_vsyscall
Oh, finally a clue: you seem to have vsyscall emulation
overhead!
Vsyscall emulation is fundamentally page fault driven - which
might explain why you are seeing page fault overhead. It might
also interact with other sources of faults - such as numa/core's
working set probing ...
Many JVMs try to be smart with the vsyscall. As a test, does the
vsyscall=native boot option change the results/behavior in any
way?
Stupid question, if you apply the patch attached below and if
you do page fault profiling while the run is in steady state:
perf record -e faults -g -a sleep 10
do you see it often coming from the vsyscall page?
Also, this:
perf stat -e faults -a --repeat 10 sleep 1
should normally report something like this during SPECjbb steady
state, numa/core:
warmup: 3,895 faults/sec ( +- 12.11% )
steady state: 3,910 faults/sec ( +- 6.72% )
Which is about 250 faults/sec/CPU - i.e. it should be barely
recognizable in profiles - let alone be prominent as in yours.
Thanks,
Ingo
---
arch/x86/mm/fault.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
Index: linux/arch/x86/mm/fault.c
===================================================================
--- linux.orig/arch/x86/mm/fault.c
+++ linux/arch/x86/mm/fault.c
@@ -1030,6 +1030,9 @@ __do_page_fault(struct pt_regs *regs, un
/* Get the faulting address: */
address = read_cr2();
+ /* Instrument as early as possible: */
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
/*
* Detect and handle instructions that would cause a page fault for
* both a tracked kernel page and a userspace page.
@@ -1107,8 +1110,6 @@ __do_page_fault(struct pt_regs *regs, un
}
}
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
-
/*
* If we're in an interrupt, have no user context or are running
* in an atomic region then we must not take the fault:
--
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