[mythtv-users] Use of fsync

[Rich Freeman]

On Tue, Oct 22, 2013 at 2:00 PM, Raymond Wagner <raymond at wagnerrp.com> wrote:
> On 10/22/2013 1:36 PM, Rich Freeman wrote:
>>
>> It would not surprise me if the right approach varies based on
>> what else is going on with the system, configuration, kernel
>> tuning, etc.
>
> MythTV (or any application) should not be manipulating system configuration
> or kernel tuning parameters on its own, and should not be given the rights
> to do so in the first place.  On the other hand, with our intended audience,
> we shouldn't be requiring users perform such tasks on their own, although
> that is a bit of an unavoidable issue regarding the external MySQL database,
> and its awful default parameters.  The right approach is the one that will
> work by default under most cases.
>

I'm not disputing that.  However, it might not hurt to make elements
of the behavior user-configurable vs requiring people to patch the
source.  I'm using Gentoo so sticking a patch file in
/etc/portage/patches/media-tv/mythtv is trivial, but those using
binary distros don't have it quite so easy.

I was doing some searching and it doesn't seem like there is actually
a great deal of discussion online around the general problem of
realtime data recording.  The other problem is that many of the tuning
parameters are system-wide.  I'm certainly interested in any info that
anybody can point me towards.  It seems like many algorithms tend to
prioritize reads since that tends to get the most work done in the
least time, but if you're recording something most of that work is
stuff that can be done at anytime, but recording is something that can
only be done NOW.

If there are application-level settings like fadvise that we could be
using, that at least would make sense.

Rich