How to measure the RAM read/write performance

[Karaoui mohamed lamine]

2013/2/27 sandeep kumar <coolsandyforyou at gmail.com>

> >"volatile" only say to the compiler to not put the variable in a register.
> >Could i ask why does you want to mesure the speed of the RAM ? Is it to
> study the NUMA behavior of the machine?
>
> In development phase of the board, we are trying to measure RAM
> performance gain while changing type of the RAM.
> The standard benchmark tools are giving us the Cache performance only. So
> we want to try some method to measure RAM performance.
>

ok.
The answear is hardware-dependent, some hardware may have a  way to disable
the cachability (but will probly need to be in the kernel).

But to skeep the hardware dependencie, you need to read a part of memory
that is not cached.
The best way is to do the test at boot time when the caches are cold. I
dont think that a user-space application could do this in precise way,
since it cannot know the physical address it address....

Doing a small "boot" code and booted directly (without grub) could give
some precise numbers.
You will also need to space yout read request (128*8 byte for example),
since most cache caches a line while you have read only one word.

Hope i helped.
regards.



>
> On Wed, Feb 27, 2013 at 2:30 PM, Karaoui mohamed lamine <
> moharaka at gmail.com> wrote:
>
>>
>>
>> 2013/2/27 sandeep kumar <coolsandyforyou at gmail.com>
>>
>>> >>I am not sure but what if you make the variable as a volatile?
>>> Hey i tried. But still is showing the same time for int & volatile int.
>>>
>>>
>> "volatile" only say to the compiler to not put the variable in a register.
>> Could i ask why does you want to mesure the speed of the RAM ? Is it to
>> study the NUMA behavior of the machine?
>>
>>
>>
>>
>>> Thanks
>>> Sandeep
>>>
>>>
>>>
>>> On Tue, Feb 26, 2013 at 6:50 PM, ankur dwivedi <ankurengg2003 at gmail.com>wrote:
>>>
>>>> I am not sure but what if you make the variable as a volatile?
>>>>
>>>> On Tue, Feb 26, 2013 at 5:01 PM, sandeep kumar <
>>>> coolsandyforyou at gmail.com> wrote:
>>>>
>>>>> Hi All
>>>>> In performance benchmark tools, When we profile read/write timings
>>>>> mostly, those read/writes are done to cache only.
>>>>>
>>>>> I want to measure my DDR(RAM chip) performance.
>>>>> So i want to make sure, every read/write should happen to DDR RAM chip
>>>>> only.
>>>>>
>>>>> How can i achieve this...Any ideas/suggestions...?
>>>>>
>>>>> --
>>>>> With regards,
>>>>> Sandeep Kumar Anantapalli,
>>>>>
>>>>> _______________________________________________
>>>>> Kernelnewbies mailing list
>>>>> Kernelnewbies at kernelnewbies.org
>>>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Thanks
>>>>
>>>> Ankur Dwivedi
>>>>
>>>>
>>>
>>>
>>> --
>>> With regards,
>>> Sandeep Kumar Anantapalli,
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>>
>>
>
>
> --
> With regards,
> Sandeep Kumar Anantapalli,
>
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