gstreamer/docs/random/ensonic/profiling.txt

92 lines
2.8 KiB
Text
Raw Normal View History

$Id$
= profiling =
== what information is interesting? ==
* pipeline throughoutput
if we know the cpu-load for a given datastream, we could extrapolate what the
system can handle
-> qos profiling
* load distribution
which element causes which cpu load/memory usage
= qos profiling =
* what data is needed ?
* (streamtime,propotion) pairs from sinks
draw a graph with gnuplot or similar
* number of frames in total
* number of audio/video frames dropped from each element that support QOS
* could be expressed as percent in relation to total-frames
* query data (e.g. via. gst-launch)
* add -r, --report option to gst-launch
* during playing we capture QOS-events to record 'streamtime,proportion' pairs
gst_pad_add_event_probe(video_sink->sink_pad,handler,data)
* during playback we like to know when an elemnt drops frames
what about elements sending a qos_action message?
* after EOS, send qos-queries to each element in the pipeline
* qos-query will return:
number of frames rendered
number of frames dropped
* print a nice table with the results
* QOS stats first
* writes a gnuplot data file
* list of 'streamtime,proportion,<drop>' tuples
= core profiling =
* scheduler keeps a list of usecs the process function of each element was
running
* process functions are: loop, chain, get, they are driven by gst_pad_push() and
gst_pad_pull_range()
* scheduler keeps a sum of all times
* each gst-element has a profile_percentage field
* when going to play
* scheduler sets sum and all usecs in the list to 0
* when handling an element
* remember old usecs t_old
* take time t1
* call elements processing function
* take time t2
* t_new=t2-t1
* sum+=(t_new-t_old)
* profile_percentage=t_new/sum;
* should the percentage be averaged?
* profile_percentage=(profile_percentage+(t_new/sum))/2.0;
* the profile_percentage shows how much CPU time the element uses in relation
to the whole pipeline
== rusage + pad-probes =
* check get_rusage() based cpu usage detection in buzztard
this together with pad_probes could gives us decent application level profiles
* different elements
* 1:1 elements are easy to handle
* 0:1 elements need a start timer
* 1:0 elements need a end timer
* n:1, 1:m and n:m type elemnts are tricky
adapter based elements might have a fluctuating usage in addition
// result data
struct {
beg_min,beg_max;
end_min,end_max;
} profile_data;
// install probes
gst_bin_iterate_elements(pipeline)
gst_element_iterate_pads(element)
if (gst_pad_get_direction(pad)==GST_PAD_SRC)
gst_pad_add_buffer_probe(pad,end_timer,profile_data)
else
gst_pad_add_buffer_probe(pad,beg_timer,profile_data)
// listen to bus state-change messages to
// * reset counters on NULL_TO_READY
// * print results on READY_TO_NULL