[arch-general] KDE plasma, baloo and UI/video playback freezes

[Francesco Porro]

Hi,

My problem is: when I'm watching a video, running Konversation in the 
background with logging on disk enabled, the playback of video slows 
down, freezes for a while.

Running iotop and ksysguard I found that baloo_file_extractor is writing 
on disk a big amount of data, filling the write queue; balooct monitor 
shows baloo is indexing Konversation's logs file changes. Peaks of 60-90 
MB/s of data on mechanical hdd are generated and the playback of videos 
(or audio, or other GUI-related tasks) slow down or freeze. Very very 
annoying.

I'm running updated versions of: KDE plasma (5.12.5), kernel (4.16.7), 
baloo (5.45); CFQ I/O scheduler on sda.

On the same machine, the same version of softwares, the same 
configurations (of programs, mounts, IO scheduler) BUT on a Debian sid 
install (home is shared between installs) is NOT showing the same issue. 
On Debian, playback is running smootly even if baloo_file_extractor is 
heavly loading IO writes queue.

On each installation I added this tweaks, to improve Vm management by 
the kernel:

[frapox at tungsteno ~]$ cat /etc/sysctl.d/local.conf 
vm.dirty_background_ratio = 2
vm.dirty_ratio = 5
vm.vfs_cache_pressure = 60

I also tried to recompile the Arch kernel with 
CONFIG_PREEMPT_VOLUNTARY=y, to reflect the same default compile setting 
of Debian, but the issue wasn't solved.

So i'm wondering which other config files or settings/tweaks I can look 
into to overcome this issue on Arch linux (I'd really love to keep on 
use Arch as my main OS).

Thanks in advance.

-- 
fp