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Message-ID: <87iqfmx3tr.fsf@depni.sinp.msu.ru>
Date: Sun, 13 Sep 2009 15:27:28 +0000
From: Serge Belyshev <belyshev@...ni.sinp.msu.ru>
To: Ingo Molnar <mingo@...e.hu>
Cc: Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Mike Galbraith <efault@....de>
Subject: Re: Epic regression in throughput since v2.6.23
Ingo Molnar <mingo@...e.hu> writes:
> Could still compare -j5 to -j4 on -tip, to see why -j4 is 3% short
> of -j5's throughput.
>
> (Plus maybe the NEW_FAIR_SLEEPERS change in -tip fixes the 3% drop.)
I've hacked the "perf" tool a bit (see the attached patch) and obtained
the following results with "perf stat -r9 make -j4 -- make clean":
--------------------------------------------------------------------------------
2.6.31-tip-01381-gf4c92b6:
Performance counter stats for 'make -j4' (9 runs):
94730.871493 task-clock-msecs # 3.503 CPUs ( +- 0.022% )
17499 context-switches # 0.000 M/sec ( +- 0.270% )
1127 CPU-migrations # 0.000 M/sec ( +- 1.159% )
4601950 page-faults # 0.049 M/sec ( +- 0.001% )
237853044260 cycles # 2510.829 M/sec ( +- 0.022% )
200554338937 instructions # 0.843 IPC ( +- 0.000% )
70615226021 cache-references # 745.430 M/sec ( +- 0.002% )
2268068445 cache-misses # 23.942 M/sec ( +- 0.020% )
27.046390652 seconds time elapsed ( +- 0.085% )
Performance counter stats for 'make -j5' (9 runs):
95283.766024 task-clock-msecs # 3.541 CPUs ( +- 0.024% )
20612 context-switches # 0.000 M/sec ( +- 0.297% )
1644 CPU-migrations # 0.000 M/sec ( +- 0.711% )
4601733 page-faults # 0.048 M/sec ( +- 0.001% )
239234709890 cycles # 2510.760 M/sec ( +- 0.024% )
200562340756 instructions # 0.838 IPC ( +- 0.000% )
70575215911 cache-references # 740.685 M/sec ( +- 0.004% )
2266361085 cache-misses # 23.785 M/sec ( +- 0.017% )
26.909772228 seconds time elapsed ( +- 0.041% )
Performance counter stats for 'make -j6' (9 runs):
95664.586804 task-clock-msecs # 3.568 CPUs ( +- 0.020% )
22358 context-switches # 0.000 M/sec ( +- 0.194% )
1835 CPU-migrations # 0.000 M/sec ( +- 0.659% )
4601777 page-faults # 0.048 M/sec ( +- 0.001% )
240188102235 cycles # 2510.732 M/sec ( +- 0.020% )
200569036210 instructions # 0.835 IPC ( +- 0.000% )
70565619805 cache-references # 737.636 M/sec ( +- 0.006% )
2265714056 cache-misses # 23.684 M/sec ( +- 0.017% )
26.808072908 seconds time elapsed ( +- 0.063% )
--------------------------------------------------------------------------------
2.6.31-tip-01385-g1ca1afc:
Performance counter stats for 'make -j4' (9 runs):
94873.128287 task-clock-msecs # 3.422 CPUs ( +- 0.020% )
13196 context-switches # 0.000 M/sec ( +- 0.181% )
1777 CPU-migrations # 0.000 M/sec ( +- 0.664% )
4601784 page-faults # 0.049 M/sec ( +- 0.001% )
238126976192 cycles # 2509.952 M/sec ( +- 0.020% )
200545291785 instructions # 0.842 IPC ( +- 0.000% )
70607104279 cache-references # 744.227 M/sec ( +- 0.005% )
2266980390 cache-misses # 23.895 M/sec ( +- 0.022% )
27.723375828 seconds time elapsed ( +- 0.134% )
Performance counter stats for 'make -j5' (9 runs):
95363.595017 task-clock-msecs # 3.519 CPUs ( +- 0.015% )
15003 context-switches # 0.000 M/sec ( +- 0.294% )
1880 CPU-migrations # 0.000 M/sec ( +- 1.017% )
4601648 page-faults # 0.048 M/sec ( +- 0.001% )
239351549481 cycles # 2509.884 M/sec ( +- 0.015% )
200552379266 instructions # 0.838 IPC ( +- 0.000% )
70576977633 cache-references # 740.083 M/sec ( +- 0.006% )
2265294365 cache-misses # 23.754 M/sec ( +- 0.012% )
27.096710006 seconds time elapsed ( +- 0.074% )
Performance counter stats for 'make -j6' (9 runs):
95739.941233 task-clock-msecs # 3.568 CPUs ( +- 0.024% )
16327 context-switches # 0.000 M/sec ( +- 0.230% )
1863 CPU-migrations # 0.000 M/sec ( +- 0.623% )
4601715 page-faults # 0.048 M/sec ( +- 0.002% )
240292969273 cycles # 2509.851 M/sec ( +- 0.024% )
200554772612 instructions # 0.835 IPC ( +- 0.000% )
70566092747 cache-references # 737.060 M/sec ( +- 0.004% )
2264738533 cache-misses # 23.655 M/sec ( +- 0.021% )
26.836474777 seconds time elapsed ( +- 0.181% )
--------------------------------------------------------------------------------
Note that the disabling NEW_FAIR_SLEEPERS doesn't fix 3% regression from
v2.6.23, but instead makes "make -j4" runtime another 2% worse (27.05 -> 27.72).
View attachment "hack-perf-stat-cleanup-command" of type "text/plain" (1717 bytes)
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