[mythtv-users] Mythfilldatabase taking FOREVER

Larry Kennedy lunchtimelarry at gmail.com
Mon Jun 20 20:22:51 UTC 2022

On Sat, Jun 18, 2022 at 1:22 PM Larry Kennedy <lunchtimelarry at gmail.com>

> On Sat, Jun 18, 2022 at 1:09 PM Gary Buhrmaster <gary.buhrmaster at gmail.com>
> wrote:
>> On Sat, Jun 18, 2022 at 1:20 PM Larry Kennedy <lunchtimelarry at gmail.com>
>> wrote:
>> > It was becoming apparent that nothing I tweaked was changing the
>> result, so I decided to stand up a new database to see.  Since I have a
>> docker platform at hand, I installed a mariadb container and loaded the
>> mythconverg database dump into that new database.  Now, MFDB runs quickly!
>> It took 30 minutes the first time since it was behind a couple of days (I
>> assume that's why), and subsequent runs are just a few minutes.  Woo Hoo!
>> Tends to support the conclusion that your issues
>> were database (configuration) related.  The need
>> for tuning for adequate performance is, as I recall,
>> one of the reasons that some MythTV elders at
>> one point proposed embedding the database
>> into the app and configuring it specifically for
>> MythTV (only) for default installs.
> I nuked and reinstalled mariadb, making sure that *everything* was cleaned
> out of /var/lib/mysql, as well as /etc/mysql/.   Even so, the reload of the
> mythconverg database dump is definitely lower than it was when I loaded the
> docker instance of the same database dump yesterday.  Clearly, there is
> something about the VM that is causing the poor performance.
>> > Where is the mythweb database config located?
>> Look inside your web server conf for settings such as:
>>    db_server "localhost"
>> the actual location and syntax will vary depending
>> on your choice of web server.
>> And, of course, you may need to be sure your
>> GRANTs are appropriate.
> OK, after much searching, I found the config file that points Mythweb to a
> database on another host.  If you run apache2 and are looking for this, go
> here:
> /etc/apache2/sites-enabled/mythweb.conf, which soft links to
> ../sites-available/mythweb.conf
> Change the setenv db_server to whatever host you run the database on.
> There are other settings like default username and password.
> And, and Gary pointed out, the database user (likely, mythtv) needs to be
> granted full permissions to mythconverg.*
> Larry

I discovered that I had a misconfigured VM that was causing the issue.  I
was able to isolate this issue by standing up an alternate database on
another platform to prove that the grabber and the sqlite database and the
number of channels were set up correctly and not part of the problem.

The configuration issue led to very expensive random I/O, which goes back
to what Gary said about the dd test and sequential I/O being different from
random I/O.


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