Re: mplayer + heavy io: why ionice doesn't help?
From: Denis Vlasenko
Date: Tue Aug 22 2006 - 12:24:43 EST
> > I eliminated skips due to CPU and disk using
> > nice and -cache 8000. I still can make it skip
> > when my KDE background picture is changing.
> I also must run mplayer at nice -20 for it to be usable.
> > I think that these skips are caused by the X server.
> > It has no prioritization for request handling and
> > thus it does not paint mplayer output fast enough:
> > it needs to repaint background and semi-transparent
> > konsole(s), and that is taking a few seconds at least.
> > This is probably aggravated by serializing nature of Xlib,
> > according to:
> > http://en.wikipedia.org/wiki/XLib
> > http://en.wikipedia.org/wiki/XCB
> I think the problem is also due to mplayer's faulty design. It should
> be multithreaded and use RT threads for the time sensitive work, like
> all professional AV applications and many other consumer players do.
RT - yes, multithreaded - unsure. Witness how squid manages to
serve hundreds of simultaneous streams using just a single process.
Multithreading seems cool on the first glance and it is easier to code
than clever O_NONBLOCK/select/poll/etc stuff. However,
on single-CPU boxes, which are still a majority, multithreading
just incurs context switching penalty. It cannot magically
make CPU do more work in a unit of time.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/