Date: 06 Jul 2005 14:26:22 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: freebsd-questions@freebsd.org Subject: Re: Weird "nice" behavior Message-ID: <44u0j7iyep.fsf@be-well.ilk.org> In-Reply-To: <pan.2005.07.06.03.56.44.535357@sremick.net> References: <pan.2005.07.06.03.56.44.535357@sremick.net>
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"Scott I. Remick" <scott@sremick.net> writes:
> I'm seeing something strange/annoying tonight... maybe someone could help
> explain why it's happening.
>
> FreeBSD 5.4-RELEASE
>
> I'm trying to do a large local rsync in the background, while listening to
> streaming audio via RealPlayer and do other stuff. I have the rsync
> running at nice level 20 ("nice -20") which I've confirmed via ps:
>
> 1001 77010 1452 0 116 20 45056 44332 select SN+ p1 0:30.89 rsync -av -
> 1001 77011 77010 295 139 20 45048 44232 - RN+ p1 20:17.12 rsync -av -
> 1001 77548 77011 0 116 20 45200 44460 select SN+ p1 0:12.06 rsync -av -
>
> RealPlayer is running at normal nice (0):
> 1001 80675 80650 16 98 0 30004 12516 select S p2 0:22.69 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80688 80675 0 96 0 30004 12516 select S p2 0:00.01 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80689 80688 0 20 0 30004 12516 pause S p2 0:02.67 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80692 80675 24 -8 0 13844 6772 piperd I p2 0:00.00 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80693 80675 24 -8 0 13844 6772 piperd I p2 0:00.00 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80694 80688 24 20 0 30004 12516 pause I p2 0:00.00 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80695 80688 0 20 0 30004 12516 pause S p2 0:01.34 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80696 80688 0 8 0 30004 12516 nanslp S p2 0:01.13 /usr/local/lib/RealPlayer/realplay.bin
> 1001 80765 80688 0 8 0 30004 12516 nanslp S p2 0:01.10 /usr/local/lib/RealPlayer/realplay.bin
>
> Not sure why it spawns so many processes, but whatever...
>
> Anyway, what's happening is despite rsync being nice 20, RealPlayer is
> incredibly choppy. Even if I'm not doing anything else on the system.
>
> Now here's the weirder part: if I DO do something, such as just scrolling
> a window, the audio stream stops being choppy. It's as if it takes some
> OTHER application claiming CPU cycles to get rsync to properly play "nice"
> and release up time, at which point RealPlayer gets the cycles it
> deserves. But for some reason, rsync with just RealPlayer on its own will
> not play "nice" and give up time to RealPlayer like it should since
> RealPlayer is running at 0 and rsync is running at 20.
Sounds like you're blocked on I/O, not CPU.
SCSI drives with tagged queueing would probably perform better.
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