On 09/26/18 04:15, Ralf Ramsauer wrote:
>
>
> On 9/26/18 12:53 PM, John Kacur wrote:
>>
>>
>> On Thu, 13 Sep 2018, Ralf Ramsauer wrote:
>>
>>> If the histogram output is enabled, cyclictest dumps lines of all latencies,
>>> even if the specific latency was never hit. For analysing a histogram, it is
>>> sufficient to only dump latencies that actually occured. This patch skips
>>> latencies that were never hit with respect to all threads.
>>>
>>> If cyclictest is used in combination with --nsecs, this removes a lot of
>>> output noise.
>>>
>>> It shrinks output to:
>>> $ cyclictest --threads 2 --affinity 2-3 --priority 99 --histofall 100 --loops 100000
>>> # /dev/cpu_dma_latency set to 0us
>>> policy: fifo: loadavg: 0.03 0.13 0.07 1/560 1248
>>>
>>> T: 0 ( 1228) P:99 I:1000 C: 100000 Min: 2 Act: 2 Avg: 2 Max: 4
>>> T: 1 ( 1229) P:99 I:1000 C: 100000 Min: 2 Act: 2 Avg: 2 Max: 4
>>> # Histogram
>>> 000002 069425 067138 136563
>>> 000003 030536 032850 063386
>>> 000004 000039 000012 000051
>>> # Total: 000100000 000100000 000200000
>>> # Min Latencies: 00002 00002
>>> # Avg Latencies: 00002 00002
>>> # Max Latencies: 00004 00004 00004
>>> # Histogram Overflows: 00000 00000 00000
>>> # Histogram Overflow at cycle number:
>>> # Thread 0:
>>> # Thread 1:
>>>
>>> Signed-off-by: Ralf Ramsauer <ralf.ramsauer@xxxxxxxxxxxxxxxxx>
>>> ---
>>> src/cyclictest/cyclictest.c | 13 ++++++++++---
>>> 1 file changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
>>> index 8d9ec80..0e8459c 100644
>>> --- a/src/cyclictest/cyclictest.c
>>> +++ b/src/cyclictest/cyclictest.c
>>> @@ -1988,16 +1988,23 @@ static void print_hist(struct thread_param *par[], int nthreads)
>>> fprintf(fd, "# Histogram\n");
>>> for (i = 0; i < histogram; i++) {
>>> unsigned long long int allthreads = 0;
>>> + unsigned long curr_latency = 0;
>>> +
>>> + for (j = 0; j < nthreads ; j++) {
>>> + curr_latency = par[j]->stats->hist_array[i];
>>> + allthreads += curr_latency;
>>> + log_entries[j] += curr_latency;
>>> + }
>>> + if (!allthreads)
>>> + continue;
>>>
>>> fprintf(fd, "%06d ", i);
>>>
>>> for (j = 0; j < nthreads; j++) {
>>> - unsigned long curr_latency=par[j]->stats->hist_array[i];
>>> + curr_latency = par[j]->stats->hist_array[i];
>>> fprintf(fd, "%06lu", curr_latency);
>>> if (j < nthreads - 1)
>>> fprintf(fd, "\t");
>>> - log_entries[j] += curr_latency;
>>> - allthreads += curr_latency;
>>> }
>>> if (histofall && nthreads > 1) {
>>> fprintf(fd, "\t%06llu", allthreads);
>>> --
>>> 2.19.0
>>>
>>>
>>
>> Note, although I initially accepted this patch I may have to revert it.
>> The output of the histogram is not consumed just by humans but by
>> software, namely rteval
>
> Narf, didn't know.
I considered commenting on this patch when it was first submitted, then
decided not to since I am no longer actively using cyclictest. But it
sounds like I can add some insight on usage of histogram data.
One of the ways that histogram data can be used is to create a line graph.
In this case, it is important to have a zero value at the beginning and
end of a range of zero values. This is maybe easiest to illustrate with
a simple data set of x (latency) and y (occurances):
1 5
2 7
3 0
4 0
5 0
6 9
7 11
8 25
9 0
If the zero values are left out, then the graph will show a straight line
from 2,7 to 6,9, which is very misleading.
When I was creating a lot of cyclictest data, I had a simple filter program
that stripped out the extraneous zero values, leaving only the first and
last zero value in a contiguous range of zero values. I did this both to
make the data files smaller (use less space and transfer faster across a
slow data link) and to make them easier to examine in a text editor.
The reason I did not speak up is that with cyclictest not outputting zero
values my filter program would simply have to be changed to sort-of the
inverse of what it does now: insert the first and last zero values.
Whether the data includes or excludes the zero data, it is a simple
filter program to transform it. Though having options to exclude
excessive zero values instead of all zero values would be a nice
feature for cyclictest. (Not volunteering to write the code. :-))
-Frank
>
>>
>> I am leaving the patch in for now and considering whether rteval could be
>> modified, but this is a heads-up.
>>
>> The other option, is for this patch to be an option
>
> Give me a couple of days and let me have a look at rteval, zero-lines
> are really useless. Maybe there's a way for rteval to support any output
> format of cyclictest.
>
> Ralf
>
>>
>> Thanks
>>
>> John
>>
>
