Re: [gentoo-user] I want to play movies without hangs

[Alex Schuster <wonko@wonkology.org>]

Michael Hampicke writes:

> Am 07.05.2012 18:26, schrieb Volker Armin Hemmann:
> > Am Montag, 7. Mai 2012, 14:41:34 schrieb Alex Schuster:
> >> Some while ago, I wrote:
> >>
> >> [
> >> mplayer stutters when I/O is going on, even hangs for seconds when I
> >> do a dd if=/dev/zero of=somefile bs=1M
> >> ]
[...]
> >> But now I found another solution: NOT USING KDE.
> >>
> >> When X crashed (trying to make the old Unreal game play), I fired up
> >> another window manager, and when I played a video in there, there
> >> was no problem at all. So, I have another workaround.
> >>
> >> But does anyone have an idea, why running KDE is the problem?
> >> Disabling desktop effects does not help.
> > 
> > nepomuk/virtuoso running in the background
> > 
> > whenever you have more than 1 process doing IO linux sucks ass.
> > 
> > Now, you write to a partition, nepomuk tries to index it (1 read) and
> > your player reading the video file (2nd read). Interactivity is shot.
> > 
> > Pause/kill nepomuk and look if it helps.

Nice shot, but this cannot be the problem. Sorry, now that I read my post
again I see I did not mention that I _still_ have KDE running all the
time, doing whatever it does. I only need to play the videos outside in a
window manager I have running in parallel.
And the output of my dd action goes to another partition anyway, which is
not being indexed. I have 280,000 files indexed, a plain locate gives
nearly ten times as much.
Virtuoso has been a big pain in the past indeed. So I had it disabled
until KDE 4.8 I think. It does some indexing now when I log in, and it is
still doing so 8 hours after I logged in the last time, but I do not
notice this much, since KDE 4.8. Whether it affects my video playback I'm
not so sure, but I have the playback problems even when it is not running
- there's too much stuff going on all the time.

> > For me the worst case is: writing lots of files on a usb device -
> > sucks everywhere, even on a vt.

Indeed. But should this affect an mplayer using a huge cache?
Does it also suck when you are writing with cp, using ionice -c 3?

> Maybe changing the kernel io scheduler will help?
> 
> # /usr/src/linux/Documentation/block/switching-sched.txt
> # /usr/src/linux/Documentation/block/deadline-iosched.txt
> # /usr/src/linux/Documentation/block/cfq-iosched.txt

Nope. I just tried noop and deadline (cfq is my default) and did not see
much of a difference.

	Wonko