i386/135447: [i386] [request] Intel Core i7 and Nehalem-EP new
features not supported
Alexander Motin
mav at FreeBSD.org
Thu Sep 23 13:10:04 UTC 2010
The following reply was made to PR i386/135447; it has been noted by GNATS.
From: Alexander Motin <mav at FreeBSD.org>
To: Dmitry Kubov <dk at garant.ru>
Cc: Andriy Gapon <avg at FreeBSD.org>, jh at FreeBSD.org,
bug-followup <bug-followup at FreeBSD.org>
Subject: Re: i386/135447: [i386] [request] Intel Core i7 and Nehalem-EP new
features not supported
Date: Thu, 23 Sep 2010 16:01:09 +0300
Dmitry Kubov wrote:
>
>> This CPU has only 266MHz TurboBoost speedup. And some part of it
>> (probably half) could be enabled all the time. This benefit still could
>> be overweighted by C-states latencies penalty. It could be interesting
>> to test some other workloads, like compilation with different number of
>> threads.
>>
>
> Actually tested 8.1-RELEASE with both TurboBoost options in BIOS:
>
> TurboBoost OFF
> Ubench Single CPU: 451935 (0.40s)
> Ubench Single CPU: 450927 (0.40s)
> Ubench Single CPU: 450486 (0.40s)
>
> TurboBoost ON
> Ubench Single CPU: 450890 (0.40s)
> Ubench Single CPU: 450890 (0.40s)
> Ubench Single CPU: 449926 (0.40s)
>
> C-states latencies penalty is reasonable idea. But looks like P0-state
> not activated at all.
Try to kill powerd and manually set highest CPU frequency. 0.40s test
time looks a bit suspicious, as powerd may just not react in time to set
P0 state.
> What about too high %% for C3 state during heavy load:
> dev.cpu.0.cx_usage: 0.17% 0.06% 99.75% last 7560us
It's not really strange. These numbers count number of enters into each
state. So when CPU is completely bust - they won't be updated. Main case
when C1 state should be actively used/counted is loads with high
interrupt rate or heavy context switching, such as disk I/O or network load.
>> Disk performance fix is reasonable. Some recent improvements in
>> 9-CURRENT should improve it even more. What's about ubench - try some
>> different load.
>>
> Can you suggest other CPU only benchmark?
>
> make -j 16 buildworld
> can't load all cores, can't see less than 11% idle
I think it's not the main goal to completely load all CPUs. But this
test is realistic and has really usable result.
--
Alexander Motin
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