linux-kernel - Re: [patch update-v1] a simple hardware detector for latency as well as throughput ver. 0.1.0

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Date:	Mon, 9 Jul 2012 20:33:23 +0800
From:	Luming Yu <luming.yu@...il.com>
To:	arnd@...db.de
Cc:	jcm@...masters.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch update-v1] a simple hardware detector for latency as well
 as throughput ver. 0.1.0

On Wed, Jun 27, 2012 at 11:00 PM, Luming Yu <luming.yu@...il.com> wrote:
> On Mon, Jun 25, 2012 at 9:37 PM, Luming Yu <luming.yu@...il.com> wrote:
>> On Tue, Jun 26, 2012 at 5:23 AM, Luming Yu <luming.yu@...il.com> wrote:
>>> The patch is the fist step to test some basic hardware functions like
>>> TSC to help people understand if there is any hardware latency as well
>>> as throughput problem exposed on bare metal or left behind by BIOS or
>>> interfered by SMI. Currently the patch tests TSC, CPU Frequency, and
>>> RDRAND, which is a new CPU instruction to get random number introudced
>>> in new CPU like Intel Ivy Bridge, in stop_machine context.
>>>
>>> The tsc samples (ns) below are from a P4 system. You can change from 0
>>> to 1000 in /sys/kernel/debug/hw_atency_test/threshold to TSC sample at ms.
>>
>> typo.
>>
>> s/ms/us/
>>
>>>
>>> [root@p4 linux]# rmmod hw_latency_test
>>> [root@p4 linux]# insmod drivers/misc/hw_latency_test.ko
>>> [root@p4 linux]# echo tsc > /sys/kernel/debug/hw_latency_test/current
>>> [root@p4 linux]# echo 1 > /sys/kernel/debug/hw_latency_test/enable
>>> [root@p4 linux]# cat /sys/kernel/debug/hw_latency_test/sample
>>> 1340657264.0434121340   388
>>> 1340657264.0935125912   379
>>> 1340657265.0436123548   404
>>> 1340657265.0937122432   441
>>> ....
>>> ^C
>>> [root@p4 linux]# echo 0 > /sys/kernel/debug/hw_latency_test/enable
>>>
>>> Signed-off-by: Luming  Yu <luming.yu@...el.com>
>>> ---
>>> I will add more tests after the first patch gets merged for those guys
>>> who want to directly play with new hardware functions, and latency and
>>> bandwidth is concern, or simply out of curiosity. The patch is based on
>>> hardware latency dector written by Jcm in RT-tree. I assume I can add
>>> Jcm's signed off here.
>>>
>>>
>>>  drivers/misc/Kconfig           |    7 +
>>>  drivers/misc/Makefile          |    2 +
>>>  drivers/misc/hw_latency_test.c |  833 ++++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 842 insertions(+), 0 deletions(-)
>>>
>>>
>>> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
>>> index c779509..a5216b5 100644
>>> --- a/drivers/misc/Kconfig
>>> +++ b/drivers/misc/Kconfig
>>> @@ -123,6 +123,13 @@ config IBM_ASM
>>>          for information on the specific driver level and support statement
>>>          for your IBM server.
>>>
>>> +config HW_LATENCY_TEST
>>> +       tristate "Testing module to detect hardware lattency and throughput"
>>> +       depends on DEBUG_FS
>>> +       depends on RING_BUFFER
>>> +       depends on X86
>
> I begun the tool on X86, but bear in mind that use standard kernel interface
> as much as possible. I was trying to measure CPU Frequency, but the use of
> calibrate_tsc forced me add a X86 dependency here.
>
> Other finding is recalibrate_cpu_khz() is a null function in SMP.
> But the only two users (p4-clockmod.c and powernow-k7.c) themselves
> could lack of users roo these days.
>
> Let me know if there are any other comments.
>
> My plan for the tool is to push it in 3.6 or 3.7. So I will routinely
> get back to the thread probably weekly or bi-weekly in the time frame.
> :-)
> The 0.2 will based on what I can see in upstream of the tool.
>
> Thanks!!!

ping Arnd,  I need to a commit ID in a tree for this work. :-)
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