> > > I have question something about selecting logic between timer-based and IRQ scheduling. > > When I tried to load 'module-alsa-sink' with 'mmap=0 tsched=1' parameters, tsched(timer-based scheduling) becomes disabled by below codes. > > It seems tsched is allowed only mmap supported ALSA devices. Why tsched disabled while use non-mmap driven ALSA? Do you meam irq mode not working well ? cat /proc/asound/card0/pcm1p/sub0/hw_params access: RW_INTERLEAVED format: S16_LE subformat: STD channels: 2 rate: 48000 (48000/1) period_size: 2048 buffer_size: 4096 Seem your sound card 16K buffer size are less than default fragment * default fragment time (100 ms) Can the driver increase periods_max ? It is impossible to rewind safely if you sound card only support two periods and DMA_RESIDUE_GRANULARITY_SEGMENT > > So, I found able to use tsched with 'mmap=0' option with below workaround code. > > I think it seems possible to use 'mmap=0 tsched=1' together. There are any reasons for that? > cat /proc/asound/card0/pcm1p/sub0/hw_params access: RW_INTERLEAVED format: S16_LE subformat: STD channels: 2 rate: 48000 (48000/1) period_size: 4096 buffer_size: 4096 Most likely your sound card need to support DMA_RESIDUE_GRANULARITY_BURST if you want to use timer scheduling <a href="http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/modules/alsa?id=051d82133f0ae6a57bf66fd200bc8e3591a7d5ca">http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/modules/alsa?id=051d82133f0ae6a57bf66fd200bc8e3591a7d5ca</a> #define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC) /* 10ms -- Sleep at least 10ms on each iteration */ #define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC) /* 4ms -- Wakeup at least this long before the buffer runs empty*/ Seem minimum latency of timer scheduling is 14ms