Discussion:
KDE plasma, baloo and UI/video playback freezes
(too old to reply)
Carsten Mattner via arch-general
2018-05-08 21:19:59 UTC
Permalink
Linux block layer's writeback system was supposed to fix this,
but I've also noticed that the mechanism isn't perfect and
you can still have a "hanging" application when doing the
infamous USB-to-USB transfer that kills the VM subsystem.
Another way I can reproduce it is when there SSD-to-thumb-drive
and you decide to some disk activity, too.
https://lwn.net/Articles/682582/
The problem is that VM gets pressured a lot and the whole
construct fails in a way, while working as designed,
manifesting as hanging programs.
Ok, but I'm talking about HDD on Sata bus. No Usb-to-usb transfers
involved. And, as said before, I've altready tweaked the
vm.dirty{writeback,background_ratio} to partialy word around this,
either on Debian or Arch linux.
It's easier to trigger with slow devices but ultimately the
same issue of block layer and vm subsystem getting overwhelmed.
First, to confirm, if you manage to run the indexer like
you would `ionice -c idle <the-indexer>`, and it shows
less hangs, you know the issue is unfair I/O queuing.
The indexer's process autostarts and rapidly kills himself in a bunch of
seconds... its impossible to renice the process, however I saw (by
Ksysguard) it's always 19 as nice value... meaning high fairness both
for the CPU, and I think for the IO too.
You can compare the block layer kernel configuration of
Debian vs Arch.
Sorry, how to? Which are the keyword for searching?
On both systems there should be /proc/config.gz of the
running kernel. If you have a suspicion which kernel
option is responsible, you can check if it's different
between Arch and Debian.
You can try deadline or bfq schedulers. One is dead simple
and the other optimizes for desktop responsiveness.
As a last chance, I'll look into these alternatives schedulers. But now,
either Debian or Arch are using the same one: Cfq. So I don't think this
is the cause of the problem.
Sounds true. Is it only that one application or others as well
when they cause much I/O?
Francesco Porro via arch-general
2018-05-27 15:43:09 UTC
Permalink
You mailed me privately. Better replying to mailing list since this could be
useful to others && please do not top quote.
Please try different i/o schedulers and maybe ck or zen kernel
for extra BFQ. But first try deadline scheduler. And, like I
suggested, check if there's a difference in process and i/o
priority between Ubuntu and Arch KDE.
How can I achieve this? I never changed the default scheduler before.

I'd prefer to stay on the default kernel, because I don't have enough
knowledge (and time or will) to maintain a custom kernel.

The priority of the Baloo scheduler is the same between Debian and derivatives
and Arch, as far as I can see.
Also, please consider filing an Arch bug with all relevant info.
Since you tested this with the same kernel version on different
distros, it's likely to be a configuration of the kernel and
applications on each distro.
Sure I'll be doing that, but before I need to get more useful data to file a
bug.
--
fp
Carsten Mattner via arch-general
2018-05-27 16:27:22 UTC
Permalink
Post by Francesco Porro via arch-general
You mailed me privately. Better replying to mailing list since this could be
useful to others && please do not top quote.
Agreed, but I only replied to your direct mail to me. Apologies if
I missed the CC somehow.
Francesco Porro via arch-general
2018-05-29 10:55:35 UTC
Permalink
Post by Carsten Mattner via arch-general
Post by Francesco Porro via arch-general
You mailed me privately. Better replying to mailing list since this could be
useful to others && please do not top quote.
Agreed, but I only replied to your direct mail to me. Apologies if
I missed the CC somehow.
You don't need to add my address since I'm subscribed to the mailing list :)
(it you do, and I hit reply, Kmail replys only to your email by default).

Btw, today i'm going to try changing the scheduler to BFQ, even if I found a
workaround that avoid the baloo scheduler activating every 10 seconds: simply
I changed the path where to save Konversation's logs to his .config dir (baloo
doen't indexes dotted files o dirs).
--
fp
Carsten Mattner via arch-general
2018-05-29 11:14:00 UTC
Permalink
Post by Francesco Porro via arch-general
You don't need to add my address since I'm subscribed to the mailing list :)
(it you do, and I hit reply, Kmail replys only to your email by default).
I think there's some confusion. I checked the mail you sent me, and
the only recipient was my address, no list addres in either field.
Therefore I assumed you mailed me directly, off-list, and so I didn't
add back the list in my reply. Usually, when someone does this, it's
considered off-list and meant to be private. It's better to miss the
list than expose a potentially personal email to the public list.

Anyway, let's focus on the topic.
Post by Francesco Porro via arch-general
Btw, today i'm going to try changing the scheduler to BFQ, even if I
Do not expect magical fixes. It may or may not help the I/O load
that's affecting you.
Post by Francesco Porro via arch-general
found a workaround that avoid the baloo scheduler activating every
10 seconds: simply I changed the path where to save Konversation's
logs to his .config dir (baloo doen't indexes dotted files o dirs).
Interesting. That sounds like a performance bug in the interaction of
Konversation and Baloo. But it's still odd that Debian doesn't have
this. I assume the KDE version tested was the same on the different
distros.
Francesco Porro via arch-general
2018-05-29 12:01:15 UTC
Permalink
Post by Carsten Mattner via arch-general
I think there's some confusion. I checked the mail you sent me, and
the only recipient was my address, no list addres in either field.
Therefore I assumed you mailed me directly, off-list, and so I didn't
add back the list in my reply. Usually, when someone does this, it's
considered off-list and meant to be private. It's better to miss the
list than expose a potentially personal email to the public list.
Can you see you (or your Mua) added my address to CC? (since the first mail I
got). If I hit reply, Kmail autofills the "To" field with your mailbox instead
of the mailinglist address, and I have to switch to ml address manually every
time (and accidentally I forgot to do it once, so you received a mail directly
from me, you assumed was a private reply). Btw, no problem.
Post by Carsten Mattner via arch-general
Interesting. That sounds like a performance bug in the interaction of
Konversation and Baloo. But it's still odd that Debian doesn't have
this. I assume the KDE version tested was the same on the different
distros.
At this point I don't know if it's a bug of baloo or konversation (or a
combination of the two), since It doesn't happen on Debian or Kubuntu. And
yes, the version of KDE and related apps were the same.
--
fp
Eli Schwartz via arch-general
2018-05-29 13:10:35 UTC
Permalink
Post by Francesco Porro via arch-general
Can you see you (or your Mua) added my address to CC? (since the first mail I
got). If I hit reply, Kmail autofills the "To" field with your mailbox instead
of the mailinglist address, and I have to switch to ml address manually every
time (and accidentally I forgot to do it once, so you received a mail directly
from me, you assumed was a private reply). Btw, no problem.
Sounds like a bug in kmail, my Thunderbird replaces the default reply
button with "Reply to list" and only sends to the list.

I actually have to go into "More" ==> "Reply all" if I want to CC people
automatically. Even the "Reply" option finds the mailinglist address as
the *From* address to reply to.
--
Eli Schwartz
Bug Wrangler and Trusted User
Jagannathan Tiruvallur Eachambadi via arch-general
2018-05-29 13:19:28 UTC
Permalink
Post by Eli Schwartz via arch-general
Post by Francesco Porro via arch-general
Can you see you (or your Mua) added my address to CC? (since the first mail I
got). If I hit reply, Kmail autofills the "To" field with your mailbox instead
of the mailinglist address, and I have to switch to ml address manually every
time (and accidentally I forgot to do it once, so you received a mail directly
from me, you assumed was a private reply). Btw, no problem.
Sounds like a bug in kmail, my Thunderbird replaces the default reply
button with "Reply to list" and only sends to the list.
Kmail has a reply to list button and it appears in the context menu as
well. I don't remember kmail having a problem earlier when I used with
respect to sending mails to a list. But this has been discussed a lot
already :P
--
Regards
Jagan
Francesco Porro via arch-general
2018-05-29 14:26:14 UTC
Permalink
In data martedì 29 maggio 2018 15:19:28 CEST, Jagannathan Tiruvallur
Post by Jagannathan Tiruvallur Eachambadi via arch-general
Post by Eli Schwartz via arch-general
Post by Francesco Porro via arch-general
Can you see you (or your Mua) added my address to CC? (since the first
mail I got). If I hit reply, Kmail autofills the "To" field with your
mailbox instead of the mailinglist address, and I have to switch to ml
address manually every time (and accidentally I forgot to do it once, so
you received a mail directly from me, you assumed was a private reply).
Btw, no problem.
Sounds like a bug in kmail, my Thunderbird replaces the default reply
button with "Reply to list" and only sends to the list.
Kmail has a reply to list button and it appears in the context menu as
well. I don't remember kmail having a problem earlier when I used with
respect to sending mails to a list. But this has been discussed a lot
already :P
Indeed. It does work properly if the sender is the mailing list address (eg.
arch-***@archlinux.org), not the private address of the author (eg frapox
at gmail dot com).
--
fp
Francesco Porro via arch-general
2018-05-29 14:30:20 UTC
Permalink
Post by Francesco Porro via arch-general
Indeed. It does work properly if the sender is the mailing list address (eg.
frapox at gmail dot com).
Sorry I was imprecise... The "reply to mailing list" of KMail works fine if
the mail you're replying to is coming from the list, not straight from the
author.
--
fp
Francesco Porro via arch-general
2018-06-02 12:11:30 UTC
Permalink
So, I finally tried the BFQ scheduler as Carsten suggested.

I tested it eg. using youtube-dl to download a big video from Vimeo (it
creates/remove quickly a lot of temp files that baloo indexes every time
causing a lot of IO), while Qbittorrent was downloading several big files...
So 100% disk activity going on (monitored with iotop).

Overloading the disk queue this way, with BFQ enabled, the result was that the
video playback of a 1080p movie by VLC was smooth and didn't hang/freeze at
all. I can assume BFQ was able to handle better all the stuff going on.

So thanks Carsten for the suggestion :) This fixed (or at least worked around)
the problem.

It remains to understand why on Debian and derivs. this issue doesn't exist.
Maybe the CONFIG_PREEMPT_VOLUNTARY=y set by default on kernel's config or some
other block device related configs I don't have the skill (and the time) to
inspect now.

Cheers
--
fp
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