Re: [Xen-devel] domU config file options for scheduling

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

As for 'cap' and 'weight', they are already configurable.
Adding the following to configuration will help.

cpu_weight = 20
cpu_cap = 50

Thanks,
Kouya

George Dunlap writes:
> I agree that there should be a way to add scheduling configuration to
> the config file.  The main wrinkle is that each scheduler takes its
> own scheduling parameters, which generally can't be translated for
> other schedulers. It would have to be up to the person making the
> config file to make sure that there were appropriate info for other
> schedulers if they might be used.
> 
> Unfortunately this would mainly have to do with python, which I'm by
> no means an expert at.  Would anyone who knows the python like to
> volunteer to do it?  Otherwise, I'll see what I can do; it shouldn't
> be too difficult to hack something together.
> 
>  -George
> 
> On Thu, Dec 10, 2009 at 7:58 AM, Thomas Goirand <thomas@xxxxxxxxxx> wrote:
> > Hi,
> >
> > This is addressed mainly to George, but maybe someone else want to work
> > on it too.
> >
> > I found very inconvenient to have to do:
> >
> > xm sched-credit -d xen08 -c 50
> >
> > after a VM starts, and I think there should be some configuration values
> > to be added into the startup file. Something like:
> >
> > shedcreditweight = 20
> > shedcreditcap = 50
> >
> > would be really useful and save a load of scripting work for everyone
> > (avoiding shell scripts to run after a VM is started).
> >
> > George, would you have time to implement this? Any chance to have this
> > added for the 4.0 release? That'd be really a GREAT addition, with I
> > believe, minimum effort.
> >
> > Also, I had a chat with George about having a kind of "burst" feature
> > added to the credit scheduler. My idea is that, by default, someone
> > would setup a credit-burst-time, and a credit-burst-cap, to any VM that
> > has a a credit-cap set. That could be set this way in the domU config file:
> >
> > shedcreditweight = 20
> > shedcreditcap = 50
> > shedbursttime = 5000 <--- 5 seconds max burst CPU time
> > shedburstcap = 80 <--- 80% CPU max during the burst
> > shedrecovertime = 2000 <--- 2 second recovery time
> >
> > Whenever a VM goes over its shedcreditcap, the burst-cap would be used
> > for a time no longer than the credit-burst-time. When this time is over,
> > then shedcreditcap would be used, until the VM uses less than
> > shedcreditcap for a time longer than shedrecovertime.
> >
> > I do believe that this kind of scheduling would be REALLY useful for
> > avoiding that a VM abuses the CPU usage. For people doing Xen VM hosting
> > business, or cloud computing, that would be just great. The values that
> > I wrote above would be a typical use.
> >
> > I had a look myself in the scheduler code, and it's quite not obvious
> > where to patch. I think I have understood the burncredit() system, but I
> > didn't get where the values are read for the cap and all. Did I
> > understood well that Xen uses 30ms cycles for the credit scheduler? If
> > that is the case, then I believe that computing what cap values to use
> > depending on the burst parameters for a given 30ms scheduling cycle
> > wouldn't be such a big overhead.
> >
> > If nobody wants to implement this, can someone gives me some pointers in
> > the sched_credit.c and all the .h structures? If I do stupid trials and
> > errors in my implementation at first, because I'd be a beginner at
> > patching Xen, would you guys have enough time to explain, and excuse a
> > newbie? Would that kind of patch be accepted if proven to work?
> >
> > Cheers,
> >
> > Thomas Goirand
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> 
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