[mythtv-users] Very slow mythfrontend, mysql at 100%

Ronald Pijnacker pijnacker at dse.nl
Fri Nov 20 14:00:16 UTC 2009

Hi Mike,

>> My primary frontend is very slow since a while.
>> Deleting recordings etc. is taking seconds, which is very annoying.
>> I noticed that mysql is at 100% cpu on the backend.
>> Could it be that over the years mythconverg has become so big that
>> this is the cause of the issue?
>> If so, which tables can I safely purge?
> No, MythTV cleans up the data in the mythconverg database--and besides, 
> myth doesn't use that much data, so even if stuff wasn't being cleaned up, 
> it wouldn't get that large.
> Something else is going on.
> I have a clean mythconverg database and get:
> # du -sh /srv/mysql/mythconverg/
> 448M    /srv/mysql/mythconverg/
> (that's 448MiB).  That's not very big from a MySQL standpoint but is 
> probably rather large from a mythconverg standpoint.  My performance is 
> fine, though.
> I'd guess it's more likely schema corruption (i.e. missing/broken indices, 
> etc.--and, yes, I saw that you said in IRC it's not crashed tables, but I 
> mean broken schema) or something.
> If you'd like to get Myth to recreate your schema (and all indices, etc.) 
> see http://www.mythtv.org/wiki/Database_Backup_and_Restore and:
>  a) Back up your DB
>  b) Drop your DB
>  c) Create a new DB with mc.sql
>  d) Create a new DB schema by running and exiting mythtv-setup
>  e) Do a partial restore ( 
> http://www.mythtv.org/wiki/Database_Backup_and_Restore#Partial_restore_of_a_backup 
> )
>  f) Run mythtv-setup to reconfigure mythbackend
>  g) Start mythbackend
>  h) Run mythfrontend and reconfigure mythfrontend and all your plugins

Since the wiki page discourages partial restores and I wasn't in the mood
to reconfigure my systems, I tried just doing a backup/restore.
I compared the first backup with a second (after restore) with identical results.
But still somehow this managed to make the problem go away!



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