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

[Mark Knecht <markknecht@gmail.com>]

On Mon, May 7, 2012 at 5:41 AM, Alex Schuster <wonko@wonkology.org> wrote:
> 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
> ]
>
>> Urs Schutz writes:
>>
>> > Just an idea: Is the disk OK? Replace /dev/sda with your
>> > disk...
> [...]
>> > I had a bad disk here, which resulted in slow IO, but not
>> > complete failure. Smart detected this immediately. Sorry,
>> > I do not know how to check disks with LVM.
>>
>> Didn't you get errors in yslog then?
>>
>> I also thought about swapping the system drive - I have a larger backup
>> drive, with nearly identical logical volumes on it, where I make
>> backups with rdiffbackup. So even the content is identical, except for
>> an additional rdiff-backup directory containing the increments. So all
>> I have to do is to echange the two volume group names, reboot, and the
>> system will run from the other drive. But I very much doubt this will
>> help, transfer speed looks okay to me, around 100 MB/s with dd.
>
> I did it in another way. I created a large file system (LVM) on my 2nd
> drive, copied /, /usr, /var, /opt and /home over. My whole system is
> encrypted, but I omitted this, just to make sure this is not the
> bottleneck.
>
> Alas, no change. Another thing I tried was to change the SATA mode in my
> BIOS from AHCI to whatever the other option is. This did not help either.
>
> Now this is really annoying. I watch small clips mostly, and can live
> with that, and when I want to watch stuff with others, I copy the file to
> tmpfs, which seems to help a lot.
>
> 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.
>
> I must be totally crazy because I still want to use KDE, despite the big
> trouble it gives me nearly every day. Yes, most things work fine now, but
> there are many many little problems, daily application crashes, and every
> time I log in I fear that the desktop won't come up. 8G of RAM was not
> enough to avoid swapping, so now I have 16G, that's fine, I no longer
> care about kwin using 1G of my RAM. Oh, and I no longer use KMail, after
> it ate thousands of mails I just wanted to move. No problem, they were
> not important, but I no longer trust the KDEPIM suite. And it seems the
> developers do not care about this, the bug report got no replies.
>
> But anyway. Any idea why it only happens with KDE? I will ask on the KDE
> mailing list, but I thought I post here first, maybe there's something
> Gentoo-specific going on here.
>
>        Wonko
>

Hey Wonko,
   OK, fire up two terminals. In one run top, hit 1 & z so you see all
your CPUs and then watch CPU usage. In the second terminal su to root
and run iotop -o. Now, watch for a few minutes and get a feel for
what's going on when video is not running. Then start your video and
watch IO usage and CPU usage. Where's the problem?

   Once you get an idea where the bottleneck is we can address what a
solution might be. In general, if the CPUs aren't maxed out and it's
an I/O problem then usually a bit more buffering is a simple solution.
Other more draconian solution might be a real-time kernel with a
player (if there is one) that is set up for real-time playback.

   Looking forward to hearing your test results.

Cheers,
Mark