Hi Bert, On Tue, 28 Mar 2017 21:15:21 -0700, Bert Schiettecatte wrote: > I'm working on a realtime audio application running on a rk3288 > platform. The application is written in the JUCE framework, and uses > ALSA for audio output. I build the application in a debian jessie > chroot since it needs a bunch of libraries compiled for armhf. > > The application used to run fine on 4.8 mainline, without noticable > audio dropouts. I had to upgrade recently to 4.10 mainline to get the > audio gadget driver working, but now the application has audio > dropouts (pause in the audio output). > > I have been using 44100 hz sample rate and 960 samples buffer size for > testing. I increased the buffer size to 1280 which seemed to improve > things a little, and then after googling around I changed the IO > scheduler to noop (it was set to CFQ), which further increases the > performance. I now only have occasional audio dropouts. > > The application does a lot of I/O via HID and has 4 audio processing > threads for signal processing, besides other threads and callbacks for > HID I/O. > > Does anyone know if there are specific settings to pay attention to > for running realtime audio processing applications on mainline 4.10, > and if anything has changed with regards to how threads are scheduled, > between 4.8 and 4.10? Just trying to understand why my application > behaves differently now on 4.10 and if this is due to changes that > have been applied and kernel config settings I might not be aware of. Are you using the RT patchset [1] and CONFIG_PREEMPT_RT_FULL? I'm able to run at 44100Hz with 128 sample buffers on RK3288 with appropriate thread priorities (although that is on a 4.4 series kernel, I haven't tested audio performance on more recent versions). You may also want the pinctrl patchset I posted recently [2] to avoid locking issues when using full RT preemption. [1] https://rt.wiki.kernel.org/index.php/Main_Page [2] https://lkml.org/lkml/2017/3/23/208 Regards, John
