[mythtv] [mythtv-commits] Ticket #1791: Stop transcode/commflag from hogging the CPU while recording/playback is in progress.

[Stuart Auchterlonie]

On Tue, Sep 19, 2006 at 03:29:52AM -0400, f-myth-users at media.mit.edu wrote:
>     > Date: Thu, 14 Sep 2006 21:22:11 +0200
>     > From: Daniel Staaf <dst at bostream.nu>
> 
>     > f-myth-users at media.mit.edu wrote:
>     > > 
>     > > Some more research -seems- to indicate that the Breezy kernel these
>     > > machines run might be fixable simply by adding
>     > >   elevator=cfq
>     > > to the boot line, and adding
>     > >   # nonaltoptions=quiet splash elevator=cfq
>     > > so it winds up on kernel updates as well.  I'm hoping that this is
>     > > true, since I'd rather not have to compile a non-stock kernel (as
>     > > your example seems to indicate).
>     > > 
>     > > It also appears I can change this on the fly with
>     > >   echo cfq > /sys/block/hdX/queue/scheduler
>     > > per-disk, and check the current setting for all disks with
>     > >   cat /sys/block/hd*/queue/scheduler
>     > > so I may be able to screw around with this without even rebooting.
> 
>     > Yes, no need to recompile.
> 
> Well, I tried "echo cfq > /sys/block/hdX/queue/scheduler", for X=a or c
> on both of my machines.  It doesn't appear to have made -any- difference;
> even though "cat /sys/block/hd*/queue/scheduler" now reported that all
> 4 disks were using CFQ, my stress-test still provoked exactly the same
> glitches when the scheduler ran, e.g., if I'm recording on multiple

Have you tried the deadline scheduler?

It guarantees i/o response within a certain timeframe (ie. deadline)
I've found it works the best for me.


Stuart