[mythtv-users] Backend going to 100% CPU

[Bob Cottingham]

On 3/31/08, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 03/31/2008 11:04 AM, Steven Adeff wrote:
> > On Sat, Mar 29, 2008 at 8:34 PM, Bob Cottingham <bobnvic at gmail.com> wrote:
> >
> >> Since upgrading to .21-fixes my backend has going to 100% CPU.  I
> >>  noticed this once when I ran mythweb, however I haven't used mythweb
> >>  since and it has happened again repeatedly. What do I need to include
> >>  if I submit a ticket? I assume that a backtrace won't show anything
> >>  since it doesn't crash.
> >>
> > first, is the version of MythWeb your running the same as the version
> > of mythbackend your running?
> > if so, try running mythbackend with the --noupnp option and see if that helps.
>
> Also, there have been reports of this happening because of problems with
> the XML-based preview request mechanism in the backend that's used by
> MythWeb.  For a while, it happened on almost every machine.  Then, the
> problem just "disappeared" for most, though no one fixed it (it's likely
> a race condition for which the timing changed just enough because of
> unrelated modifications to Myth to prevent the problem on some
> machines).  However, one person--the author of MythWeb, Chris
> Petersen--has actually seen it since.  You may be the second person.  If
> it's 100% reproducible by just requesting XML previews repeatedly, you are.
>
> If you want to find out, feel free to run the attached (hack of a)
> script (when the backend isn't running at 100%) to see if it causes the
> CPU to max out (make an empty temp directory from which to run it as it
> will drop a bunch of previews in the dir).  If so, you might be able to
> work around the problem by changing the timing on your backend machine a
> bit (i.e. by underclocking it a little or something).  Note that this
> script is meant only as a diagnostic tool and is not developed to be
> generally useful.  It has some stuff hardcoded, so you may need to
> modify it a bit.
>
> Mike
{script deleted}

Unfortunately, I couldn't get the script to work. I just get
permission errors, even when running as root. I don't know perl and I
don't really know what might need to be changed beyond replacing the
first instance of {HOST} with the IP address of the machine.

I've avoided using mythweb since the first time I noticed it sent the
backend to 100%, yet I still find the backend going to 100% after a
few hours, so mythweb can't be the only problem.

Since I'm also experiencing some other issues which I havn't seen
anyone else complaining about, I may try wiping my source tree and
downloading a fresh copy and recompiling.  I followed svn for a while
where several of these issues were noted, so perhaps I just don't have
a clean copy.

Thanks for your help,
Bob C