Date: Sat, 29 Oct 2005 01:06:36 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: Pertti Kosunen <pertti.kosunen@pp.nic.fi>, David Xu <davidxu@freebsd.org>, "Yuriy N. Shkandybin" <jura@networks.ru>, current@freebsd.org Subject: Re: Timers and timing, was: MySQL Performance 6.0rc1 Message-ID: <20051029010225.P20147@fledge.watson.org> In-Reply-To: <35696.1130538037@critter.freebsd.dk> References: <35696.1130538037@critter.freebsd.dk>
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On Sat, 29 Oct 2005, Poul-Henning Kamp wrote:
> You forgot to tell us what
>
> sysctl kern.timecounter.hardware
>
> was on the machine, but I pressume ACPI-fast ?
Yes:
kern.timecounter.hardware: ACPI-fast
kern.timecounter.choice: TSC(-100) ACPI-fast(1000) i8254(0)
dummy(-1000000)
With TSC on SMP, you see the expected sorts of results:
x 7SMP/clock_gettime_realtime
+ 7SMP/TSC_clock_gettime_realtime
* 7SMP/clock_gettime_poor
+--------------------------------------------------------------------------+
|* + x|
|* + x|
|* * + x x|
|* * + x x|
|* * + x x|
|** ** ++ xx xx|
||MA_| |A| |A_M|
+--------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 12 1404 1450 1444 1430.0833 19.327128
+ 12 571 623 616 612.91667 13.627901
Difference at 95.0% confidence
-817.167 +/- 14.1587
-57.1412% +/- 0.990063%
(Student's t, pooled s = 16.7221)
* 12 503 566 517 527.08333 26.352362
Difference at 95.0% confidence
-903 +/- 19.5659
-63.1432% +/- 1.36817%
(Student's t, pooled s = 23.1083)
Robert N M Watson
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