[mythtv-users] Bad mysql performance -- huge oldrecorded -- joins without index

[Michael T. Dean]

On 06/08/2016 10:42 AM, Simon Hobson wrote:
> "Michael T. Dean" wrote:
>
>> There is one way to improve scheduler performance outside of MythTV--4) throw more/better resources at it:  get better/more CPU and/or RAM and/or file system performance (which can have a huge impact if using things like barriers or file systems that take huge amounts of I/O resources when doing things like deleting large files and when the user didn't enable slow deletes in MythTV, like he should have).
> So the first step is, as the OP seems already to be doing, tune MySQL to the load and use as much RAM as "makes sense" - there is a point where adding RAM makes little additional difference, but initially a bit more RAM can make a huge difference.

Yes, this is definitely important, too--and may well be a large part of 
the problem.  There's nothing MythTV is doing that requires a 
supercomputer, so given a reasonable computer for running MythTV, 
performance should be good for any "residential" use case.

I will also say that file system choice/configuration (especially in 
regards to blocking due to barriers***) for the file system holding the 
MySQL binary data files and MySQL configuration (especially with the 
much-more-difficult-to-properly-configure-for-reasonable-performance 
InnoDB storage engine that many are using) are often bad on many systems 
out there.  That said, a proper discussion of the 
issues/considerations/... involved when it comes to MySQL would make my 
previous reply (a short novel), which focused only on the MythTV-related 
aspects, look like a short tweet in comparison. Therefore, I took the 
easy way out and ignored the MySQL aspect.

Mike

*** Note, too, that I am not saying to disable barriers on the file 
system used to store MySQL data files, nor on any other.