Re: [Powerpc-utils-devel] [PATCH] Fix ppc64_cpu --threads-per-core when --smt value set

[Vasant H. <heg...@li...>]

On 01/08/2015 01:33 AM, Nathan Fontenot wrote:
> On 01/07/2015 01:01 AM, Vasant Hegde wrote:
>> On 12/23/2014 12:08 PM, Mamatha Inamdar wrote:
>>> Problem: ppc64_cpu --threads-per-core gives wrong data when --smt value set
>>>
>>> This patch will resolve the above issue and display the correct values of threads-per-core
>>> for the ppc64_cpu command when --smt value is set.
>>>
>>> I have used the following equation to calculate threads_per_core as per lscpu command.
>>>
>>> 	threads_per_core = nthreads / ncores
>
> I think there may be a slight misunderstanding between the threads-per-core
> option for the ppc64_cou command and what lscpu reports.
>
> The threads-per-core option to the ppc64_cpu command reports the number of
> threads that a core contains, not the number of online threads per core.
>
> If you want to know the number of online threads per core you need to use the
> --info or --smt option.

I think we need man page for this command!


-Vasant


>
> -Nathan
>
>>>
>>> ***********************************************
>>> Test results:
>>>
>>> CASE 1:
>>>
>>> ./src/ppc64_cpu --smt=on
>>> [root@llmjuno03b powerpc-utils]# ./src/ppc64_cpu --threads-per-core
>>> Threads per core: 4
>>>
>>> lscpu output:
>>> Thread(s) per core:    4
>>> ------------------------------------------
>>> CASE 2:
>>>
>>> ./src/ppc64_cpu --smt=2
>>> [root@llmjuno03b powerpc-utils]# ./src/ppc64_cpu --threads-per-core
>>> Threads per core: 2
>>>
>>> lscpu output:
>>> Thread(s) per core:    2
>>> --------------------------------------------------
>>> CASE 3:
>>>
>>> ./src/ppc64_cpu --smt=1
>>> [root@llmjuno03b powerpc-utils]# ./src/ppc64_cpu --threads-per-core
>>> Threads per core: 1
>>>
>>> lscpu output:
>>> Thread(s) per core:    1
>>> -------------------------------------------------
>>>
>>> Signed-off-by: Mamatha Inamdar <mam...@li...>
>>> ---
>>>    src/ppc64_cpu.c |   15 ++++++++++++++-
>>>    1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/ppc64_cpu.c b/src/ppc64_cpu.c
>>> index 4df4cdc..a3cfed0 100644
>>> --- a/src/ppc64_cpu.c
>>> +++ b/src/ppc64_cpu.c
>>> @@ -56,6 +56,7 @@ static int counters[MAX_NR_CPUS];
>>>    static int threads_per_cpu = 0;
>>>    static int cpus_in_system = 0;
>>>    static int threads_in_system = 0;
>>> +static int threads_per_core = 0;
>>
>> Why do you need another global variable ? can't you just print " nthreads /
>> cpus_in_system" ?
>>
>>>
>>>    static int do_info(void);
>>>
>>> @@ -529,9 +530,21 @@ static int do_smt(char *state)
>>>    	return rc;
>>>    }
>>>
>>> +/* Threads per core */
>>>    static inline void do_threads_per_core()
>>>    {
>>> -	printf("Threads per core: %d\n", threads_per_cpu);
>>> +	int i, j;
>>> +	int nthreads;    /* number of threads online */
>>
>> initialize nthreads ?
>>
>>
>>> +
>>> +	/* Calculate number of threads present on the system */
>>> +	for (j = 0; j < threads_in_system; j += threads_per_cpu) {
>>> +		for (i = 0; i < threads_per_cpu; i++)
>>> +			nthreads += cpu_online(j + i);
>>> +	}
>>
>> Can we have different cores with different SMT level?
>>
>> -Vasant
>>
>>> +
>>> +	/* Calculate threads per core = nthreads / ncores */
>>> +	threads_per_core = nthreads / cpus_in_system;
>>> +	printf("Threads per core: %d\n", threads_per_core);
>>>    }
>>>
>>>    static int do_subcores_per_core(char *state)
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Dive into the World of Parallel Programming! The Go Parallel Website,
>>> sponsored by Intel and developed in partnership with Slashdot Media, is your
>>> hub for all things parallel software development, from weekly thought
>>> leadership blogs to news, videos, case studies, tutorials and more. Take a
>>> look and join the conversation now. http://goparallel.sourceforge.net
>>> _______________________________________________
>>> Powerpc-utils-devel mailing list
>>> Pow...@li...
>>> https://lists.sourceforge.net/lists/listinfo/powerpc-utils-devel
>>>
>>
>>
>> ------------------------------------------------------------------------------
>> Dive into the World of Parallel Programming! The Go Parallel Website,
>> sponsored by Intel and developed in partnership with Slashdot Media, is your
>> hub for all things parallel software development, from weekly thought
>> leadership blogs to news, videos, case studies, tutorials and more. Take a
>> look and join the conversation now. http://goparallel.sourceforge.net
>> _______________________________________________
>> Powerpc-utils-devel mailing list
>> Pow...@li...
>> https://lists.sourceforge.net/lists/listinfo/powerpc-utils-devel
>>