On 06.02.2015 11:02, Alexander E. Patrakov wrote:
> 06.02.2015 14:56, Georg Chini wrote:
>> One more thing: There is a systematic error in the adjust_time I could
>> not work around without
>> introducing too much overhead. The latency snapshot varies widely in the
>> execution time, I
>> measured values between 50 us and more than 60 ms. So if the extreme
>> values follow each other
>> you will have one adjust time that is around 60 ms too long and another
>> one which is 60 ms too
>> short. Maybe this also contributes significantly to the (in)stability of
>> regulation.
>
> Thanks for this observation. I will look into it, too.
>
I just ran perf to look at the difference between using module-loopback with
"latency_msec=10" and "latency_msec=6 buffer_latency_msec=4". I cannot
clock down my CPU, it is an Atom board. Top shows about 14% CPU with the
first option and 9% with the second option.
With perf I cannot see where this difference comes from:
latency_msec=10 (everything below 0.5% omitted):
2,67% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x000000000000985d
2,11% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x0000000000009855
1,92% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x000000000000984c
1,88% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x0000000000009844
1,71% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x000000000000986d
1,24% alsa-sink-ALC88 [snd_hda_intel] [k]
0x00000000000000a7
0,74% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x0000000000009858
0,66% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x000000000000984f
0,52% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.]
0x0000000000009861
latency_msec=6 buffer_latency_msec=4 (everything below 0.5% omitted):
3,51% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x000000000000985d
2,64% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009855
2,45% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009844
2,44% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x000000000000984c
2,29% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x000000000000986d
1,83% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009a02
1,69% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009a11
0,99% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009858
0,97% alsa-sink-ALC88 [snd_hda_intel] [k] 0x00000000000000a7
0,87% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x000000000000984f
0,69% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009a2f
0,61% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009861
0,54% alsa-sink-ALC88 libspeexdsp.so.1.5.0 [.] 0x0000000000009a2c
As there seem to be less overall busy cycles in the second case the
somewhat higher
(instead of lower as expected) numbers can be explained by that.
