[mythtv-users] Weird behavior with top

[Aran]

On Fri, 2004-10-29 at 18:09, Matt Vollmar wrote:

> On my box, for some really odd reason, when Myth is the one taking the 
> CPU (front or backend), top does not show the top running process.  This 
> seems really strange.  If I sort by CPU, nothing comes to the top that 
> is above 5%!  I thought maybe this was some weird glitch with top, but 
> then I was just gzip'ing a large file and gzip was taking 45% of the 
> CPU.  I thought, "That's odd."  I checked and sure enough, Myth was 
> recording something.  I stopped the recording and suddenly gzip was 
> taking 95% of the CPU.  Is this normal behavior that all of you see on 
> your boxen?  I am starting to wonder if I am missing some critical 
> multi-threading library or something.  Or, my box could be 
> demon-possessed and need an exorcism.  Who knows???

CPU time is not the only resource that processes compete over, memory
and various kinds of I/O are others.  Perhaps you have your disk
configured incorrectly, that is it isn't in the proper UDMA mode or
something similar.  If mythbackend was writing to the disk, maybe gzip
couldn't read and write the data it was compressing fast enough to
completely utilize the CPU, hence it only showed 45%.

You should try reading the hdparm man page for making sure your disk is
configured correctly. Also, try looking at the output of vmstat 2 while
this is going on.  vmstat will show you whether or not you are paging
(aka swapping, though paging is technically correct), how much disk i/o
there is on the system, etc.

Perhaps all this was covered in your previous attempts at seeking help,
but good luck either way!