linux-kernel - Re: [RFT] Please test rdtsc on various x86-64 hardware (app included)

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Message-ID: <20110418221051.GR16484@one.firstfloor.org>
Date:	Tue, 19 Apr 2011 00:10:51 +0200
From:	Andi Kleen <andi@...stfloor.org>
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)

I tested it on a dual Westmere-EP and a Quad Westmere-EX.
Seems to pass everywhere.

However I kept the default MAX_THREADS 4. Shouldn't that be 
increased for the large systems?

I suspect the tests as written didn't really use the large 
systems.

Dual:

CPU vendor   : GenuineIntel
CPU model    : Intel(R) Xeon(R) CPU           E5640  ...
CPU stepping : ..
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 failed  : worst error 48 with 48647928 samples
Load3 test passed: margin 368 with 1013805 samples
Load test passed : margin 368 with 4142659 samples
Store test failed as expected: worst error 2940 with 4298473 samples

Quad:

CPU vendor   : GenuineIntel
CPU model    : Intel(R) Xeon(R) CPU E7 ...
CPU stepping : ..
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 208 with 11997136 samples
Load3 test passed: margin 812 with 98710 samples
Load test passed : margin 208 with 1259451 samples
Store test failed as expected: worst error 9284 with 1086616 samples

-Andi
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