Re: Understanding perf mem -t load results

[Manuel Selva <selva.manuel@gmail.com>]

Thanks,

"You cannot use uncore events to sample IPs" means that the values 
corresponding to PERF_SAMPLE_IP are not correct ? Some benchmarks I did 
by sampling ME_INST_RETIRED with PERF_SAMPLE_IP let me think that I was 
able to get the source of th event. The IP value was coherent. Maybe 
this is not always the case.

I am thus going to look a offcore request to sample remote memory 
accesses with correct IPs values.

Manu

On 12/24/2013 03:18 AM, Andi Kleen wrote:
>> In my experiments I get LFB samples with weight equal or greater than
>> local RAM samples, I should I interpret these values ?
>
> The measured latency can include the pipeline latency.
>
>> Moreover, because I am more interested in identifying remote memory
>> accesses sources than in effective load latency weight, I am wondering
>> if using the perf mem tool (using the
>> MEM_INST_RETIRED.LATENCY_ABOVE_THRESHOLD event) is the best solution.
>> Couldn't I use sampling on other events such as UNCORE ones more
>> easily and efficiently ?
>
> You cannot use uncore events to sample on IPs.
>
> -Andi
>