[mythtv] Loud hard drive due to NuppelVideoRecorder.cpp sync()

Sam N. Max (snx) snx at rogers.com
Fri Jun 13 03:49:00 EDT 2003


Thanks, didn't know about that option.  Unfortunately this is a somewhat
old drive I'm dealing with (quantum fireball plus lm), and from what I
can tell it doesn't support this (hdparm returns 0).  The drive was at the
time considered quiet, it's just when it's forced to seek (noticed that an
review on StorageReview.com mentions this flaw in it it's conclusion).

- Eron

----- Original Message ----- 
From: "Arthur Britto" <ahbritto at iat.com>
To: "Development of mythtv" <mythtv-dev at snowman.net>
Sent: Friday, June 13, 2003 1:44 AM
Subject: Re: [mythtv] Loud hard drive due to NuppelVideoRecorder.cpp sync()


> Another option to quiet newer IDE drives would be to use the -M option
> of hdparm.
>
> -Arthur
>
> On Thu, 2003-06-12 at 22:25, Sam N. Max (snx) wrote:
> > I am fairly new to MythTV, so please bare with me... :)
> >
> > During recording or live recording my hard drive was getting very loud
> > writing little bits of the video to the hard drive every second.  After
a
> > while I figured out that this had to do with the call to sync() in
> > NuppelVideoRecorder::WriteVideo which gets called every keyframe (which
is
> > every second).  I imagine this was done to try to spread the load of any
> > hard drive writes so there isn't a large write later on.  I commented
the
> > sync() out, and my hard drive settled down, and from what I can tell I
> > wasn't having any trouble recording.
> >
> > I'm not sure if I'm the only one has this hard drive noise problem.
It's
> > not as big a problem when it's writing a long stream of bytes (i.e. a
> > copying a huge file), but it has a problem with writing small bits every
> > second as myth does.  Looking at the man page for sync() this causes
myth to
> > wait, which may end up wasting CPU time that could have been used
encoding
> > while the data gets sent to the hard drive (unless there's some
> > multithreading going on to get around this).
> >
> > Perhaps an option could be added to allow the user to specify whether
sync()
> > should be called.  I'm not sure about other users experiences, but it
might
> > make sense to not have it all (or default off).  If it used, there might
be
> > some gain in encoding speed by moving the call to sync into another
thread,
> > though that may prove useless.
> >
> > One final thought.  Many people seem to have noticed a slow down with
> > version 0.9 (for now I've been sticking with 0.8).  I haven't fiddled
with
> > it yet, but I was wonderring if the "position map" database write that
> > occurs every key frame may be the culprit (it comes right after the
sync()
> > call in NuppelVideoRecorder.cpp).  There's also the call to the somewhat
> > kludgy looking "KickDatabase" function which I'm not totally sure
about...
> > ;)
> >
> > - Eron
> >
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