[mythtv-commits] Ticket #3757: Reduce polling in mythwelcome

[MythTV]

#3757: Reduce polling in mythwelcome
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 Reporter:  anonymous  |        Owner:  ijr 
     Type:  defect     |       Status:  new 
 Priority:  minor      |    Milestone:  0.21
Component:  mythtv     |      Version:  head
 Severity:  low        |   Resolution:      
  Mlocked:  0          |  
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Comment(by drees76 at gmail.com):

 Replying to [comment:11 candrews at integralblue.com]:
 > According to powertop, the backend's polling rate stayed the same at
 ~16.5/sec on my computer.
 > However, it helped in your setup (as it seems it did!) then that's even
 better!

 You'll notice in your "before" mythbackend shows up twice, once with 75
 wu/s (schedule_timeout) and once with 16 wu/s (futex_wait). Your "after"
 plot eliminates the mythbackend schedule_timeout wakeups completely which
 is expected from the patch.

 The mythbackend futex_wait wakeups are coming from somewhere else.

 > I've been running the patch since I applied it on a backend/frontend
 combo, and on a frontend
 > only. I haven't noticed any bugs, and I've been using both to watch and
 record tv, do live tv,
 > watch videos, etc.

 Great! That's what I expected. Hopefully the devs can push this patch
 upstream!

 > As for the strace, that was taken with the patch applied. I'm presently
 trying to figure out
 > how to use gdb to figure out where in the code those selects are taking
 place, but not being a
 > C programmer or someone who has ever used gdb is making that difficult
 :-)

 The other way is to simply read the code and look for places where polling
 out timeouts are used, but without being a C/C++ or a programmer at all
 makes it a bit difficult. :-)

 I haven't used gdb in a while myself, but what needs to be done is to
 attach the process to the debugger and then print out a stack trace of all
 the running threads. It should be apparent what threads are doing the
 polling.

-- 
Ticket URL: <http://svn.mythtv.org/trac/ticket/3757#comment:12>
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