[mythtv-users] Weird behavior with top

[Brian Foddy]

On Friday 29 October 2004 11:26 pm, Aran wrote:
> 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!

I've noticed this too, I attributed it to that top hasn't caught up to
the multi-threaded behavior of linux 2.6.  GZIP is a nice single thread
that top understands.  Under 2.4, top showed myth processes correctly.
At least that is my theory...

Brian