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Date: Tue, 19 Apr 2011 03:49:00 +0300 From: Mihai Donțu <mihai.dontu@...il.com> To: Andrew Lutomirski <luto@....edu> Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>, Linus Torvalds <torvalds@...ux-foundation.org>, Andi Kleen <andi@...stfloor.org>, x86 <x86@...nel.org> Subject: Re: [RFT] Please test rdtsc on various x86-64 hardware (app included) On Mon, 18 Apr 2011 15:32:52 -0400 Andrew Lutomirski <luto@....edu> wrote: > Hi all- > > I'd appreciate some help testing rdtsc's ordering wrt memory on > various hardware. You can download evil-clock-test code at: > > https://gitorious.org/linux-test-utils/linux-clock-tests/blobs/raw/master/evil-clock-test.cc On my laptop: $ dmesg | grep -i tsc [ 0.000000] Fast TSC calibration using PIT [ 0.099991] TSC synchronization [CPU#0 -> CPU#1]: [ 0.099991] Measured 3156958390 cycles TSC warp between CPUs, turning off TSC clock. [ 0.099991] Marking TSC unstable due to check_tsc_sync_source failed $ ./a.out CPU vendor : GenuineIntel CPU model : Intel(R) Core(TM)2 CPU T5500 @ 1.66GHz CPU stepping : 6 TSC flags : tsc constant_tsc Using lfence_rdtsc because you have an Intel CPU Will test the "lfence;rdtsc" clock. Now test passed : margin 200 with 17193024 samples Load3 test passed: margin 23270 with 45 samples Load test passed : margin 70 with 3704403 samples Store test failed as expected: worst error 50 with 3535212 samples On a colleague's laptop: $ dmesg | grep -i tsc [ 0.000000] Fast TSC calibration using PIT [ 0.339747] Marking TSC unstable due to TSC halts in idle $ ./a.out CPU vendor : GenuineIntel CPU model : Intel(R) Core(TM)2 Duo CPU T9300 @ 2.50GHz CPU stepping : 6 TSC flags : tsc constant_tsc Using lfence_rdtsc because you have an Intel CPU Will test the "lfence;rdtsc" clock. Now test passed : margin 87 with 44323872 samples Load3 test passed: margin 32062 with 28 samples Load test passed : margin 62 with 14113177 samples Store test failed as expected: worst error 850 with 12444429 samples One of the servers I have around (2 x 6 core + HT): $ dmesg | grep -i tsc [ 0.000000] Fast TSC calibration using PIT [ 0.398130] checking TSC synchronization [CPU#0 -> CPU#1]: passed. [ 0.577634] checking TSC synchronization [CPU#0 -> CPU#2]: passed. [ 0.757168] checking TSC synchronization [CPU#0 -> CPU#3]: passed. [ 0.936733] checking TSC synchronization [CPU#0 -> CPU#4]: passed. [ 1.116321] checking TSC synchronization [CPU#0 -> CPU#5]: passed. [ 1.295821] checking TSC synchronization [CPU#0 -> CPU#6]: passed. [ 1.475418] checking TSC synchronization [CPU#0 -> CPU#7]: passed. [ 1.654917] checking TSC synchronization [CPU#0 -> CPU#8]: passed. [ 1.834550] checking TSC synchronization [CPU#0 -> CPU#9]: passed. [ 2.014061] checking TSC synchronization [CPU#0 -> CPU#10]: passed. [ 2.193601] checking TSC synchronization [CPU#0 -> CPU#11]: passed. [ 2.373170] checking TSC synchronization [CPU#0 -> CPU#12]: passed. [ 2.552713] checking TSC synchronization [CPU#0 -> CPU#13]: passed. [ 2.732212] checking TSC synchronization [CPU#0 -> CPU#14]: passed. [ 2.911760] checking TSC synchronization [CPU#0 -> CPU#15]: passed. [ 3.091288] checking TSC synchronization [CPU#0 -> CPU#16]: passed. [ 3.270920] checking TSC synchronization [CPU#0 -> CPU#17]: passed. [ 3.450454] checking TSC synchronization [CPU#0 -> CPU#18]: passed. [ 3.629995] checking TSC synchronization [CPU#0 -> CPU#19]: passed. [ 3.809492] checking TSC synchronization [CPU#0 -> CPU#20]: passed. [ 3.989045] checking TSC synchronization [CPU#0 -> CPU#21]: passed. [ 4.168647] checking TSC synchronization [CPU#0 -> CPU#22]: passed. [ 4.348183] checking TSC synchronization [CPU#0 -> CPU#23]: passed. [ 4.577658] Switching to clocksource tsc $ ./a.out CPU vendor : GenuineIntel CPU model : Intel(R) Xeon(R) CPU X5650 @ 2.67GHz CPU stepping : 2 TSC flags : tsc rdtscp constant_tsc nonstop_tsc Using lfence_rdtsc because you have an Intel CPU Will test the "lfence;rdtsc" clock. Now test passed : margin 233 with 32792352 samples Load3 test passed: margin 193 with 1912536 samples Load test passed : margin 85 with 4347111 samples Store test failed as expected: worst error 1996 with 3920055 samples -- Mihai Donțu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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