Running mpv in isolated core.

[tramchamploo]

Hi, I'm trying to run mpv in Linux with isolated cores for jitter free playback. I'm using realtime kernel and isolate mpv with nohz_full and rcu_nocbs then cpuset to make it exclusive on specific cores. I'm only playing audio, the playback went smoothly at first but cpu usage went high every few seconds leading to a device underrun. I don't want to make buffer large because small buffer and period helps with my dac's PLL circuit for lowest jitter.
I noticed cpu goes high at the moment that playback time updates. On a tickless core, playback time hardly updates but once it does, it blocks the playback. I suspected it's time retrieval that causes the lag. I did some code digging and found mpv already uses CLOCK_MONOTONIC_RAW as clocksource. . So I make tsc=reliable and tsc=nowatchdog for system to only get timestamp via tsc instead of trying to sync with other clocksource like hpet every now and then. I also tried osd-level=0 to suspend UI updates. It went no luck and the issue persist.
So it can be other operations near the time retrieval that causes blocking. Another thing is I use very long tap resampling with libavfilter in my mpv config, after disabling threading of filtering, things got better but not completely resolved. I know rt threads tend to run exclusively without giving timeslice to other tasks but how can I improve the situation?