Re: Scheduler ( was: Just a second ) ...

[Peter Wächtler]

Doug Ledford schrieb:
> 
> Andreas Dilger wrote:
> 
> > On Dec 18, 2001  09:27 -0800, Linus Torvalds wrote:
> >
> >>Maybe the best thing to do is to educate the people who write the sound
> >>apps for Linux (somebody was complaining about "esd" triggering this, for
> >>example).
> >>
> >
> > Yes, esd is an interrupt hog, it seems.  When reading this thread, I
> > checked, and sure enough I was getting 190 interrupts/sec on the
> > sound card while not playing any sound.  I killed esd (which I don't
> > use anyways), and interrupts went to 0/sec when not playing sound.
> > Still at 190/sec when using mpg123 on my ymfpci (Yamaha YMF744B DS-1S)
> > sound card.
> 
> Weel, evidently esd and artsd both do this (well, I assume esd does now, it
> didn't do this in the past).  Basically, they both transmit silence over the
> sound chip when nothing else is going on.  So even though you don't hear
> anything, the same sound output DMA is taking place.  That avoids things
> like nasty pops when you start up the sound hardware for a beep and that
> sort of thing.  It also maintains state where as dropping output entirely
> could result in things like module auto unloading and then reloading on the
> next beep, etc.  Personally, the interrupt count and overhead annoyed me
> enough that when I started hacking on the i810 sound driver one of my
> primary goals was to get overhead and interrupt count down.  I think I
> suceeded quite well.  On my current workstation:
> 
> Context switches per second not playing any sound: 8300 - 8800
> Context switches per second playing an MP3: 9200 - 9900
> Interrupts per second from sound device: 86
> %CPU used when not playing MP3: 0 - 3% (magicdev is a CPU pig once every 2
> seconds)
> %CPU used when playing MP3s: 0 - 4%
> 
> In any case, it might be worth the original poster's time in figuring out
> just how much of his lost CPU is because of playing sound and how much is
> actually caused by the windowing system and all the associated bloat that
> comes with it now a days.
> 

Do you really think 8000 context switches are sane?

pippin:/var/log # vmstat 1
   procs                      memory    swap          io     system         cpu
 r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  us  sy  id
 2  0  0 100728   4424 121572  27800   0   1     6     6   61    77  98   2   0
 2  0  0 100728   5448 121572  27800   0   0     0    68  112   811  93   7   0
 2  0  0 100728   5448 121572  27800   0   0     0     0  101   776  95   5   0
 3  0  0 100728   4928 121572  27800   0   0     0     0  101   794  92   8   0

having a load ~2.1 (2 seti@home)