Re: Making nice niser for system hogging programs

[Jens Axboe]

On Tue, Oct 04 2005, Matt Helsley wrote:
> On Sun, 2005-10-02 at 13:07 +1000, Con Kolivas wrote:
> > On Sun, 2 Oct 2005 12:26, Marc Perkel wrote:
> > > Just a thought -----
> > >
> > > Programs like cp -a /bigdir /backup and rsync usually bring the server
> > > to a crawl no matter how much "nice" you put on them. Is there any way
> > > to make "nice" smarter in that it limits io as well as processor usage?
> > > If cp and rsyne ran a little slower IO wise then everything else could
> > > run too.
> > 
> > The latest cfq io scheduler supports io nice levels. By default it links the 
> > io nice levels to the cpu nice levels so if you use cfq and set your file 
> > commands nice 19 they will use as little io priority as possible. Note this 
> > only works on the read side but that makes a dramatic difference already.
> > 
> > Cheers
> > Con
> 
> 	If you want a way to assign io priorities without relying on process
> inheritance and (re)nice you might find CKRM, with it's cfq-based IO
> controller, useful.
> 
> 	Basically you create a set of classes that group tasks and give an
> appropriate share of IO performance to tasks in that class. As processes
> get created CKRM will assign tasks to the IO classes based on a set of
> rules. You can run commands like:
> 
> mkdir /rcfs/taskclass/makin_copies
> echo 'res=io,guarantee=20' > /rcfs/taskclass/makin_copies/shares
> echo 'path=/usr/bin/rsync,class=makin_copies' > /rcfs/ce/rsync_rule
> echo 'path=/bin/cp,class=makin_copies' > /rcfs/ce/cp_rule
> 
> to set this up. This should make CKRM useful for those unwilling to
> become full-time administrators just to run their own desktops.

Has the CKRM io controller been updated to 2.6.13 level CFQ, or is it
still using the very basic per-request based io sharing?

-- 
Jens Axboe

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