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SubjectRe: [RFT] Please test rdtsc on various x86-64 hardware (app included)
On Mon, 18 Apr 2011 15:32:52 -0400 Andrew Lutomirski <luto@mit.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
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