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buildd queue starvation (Was: Re: Do not make gratuitous source uploads just to provoke the buildds!)

On Sun, Mar 13, 2005 at 11:43:41AM +1100, Matthew Palmer wrote:
> On Sat, Mar 12, 2005 at 04:24:35PM -0800, Thomas Bushnell BSG wrote:
> > What are these "relatively effective workarounds"?
> Not being a buildd admin, I have no idea as to the specifics, but I infer
> the existence of these workarounds due to the fact that, on the whole, the
> build queues don't appear to suffer from hideous starvation problems.

Apparantly an explanation is needed here:
- normally, buildd power is more than new packages getting uploaded
  (otherwise, queue would only be growing, and never reduce)
- as a consequence, normally the Needs-Build queue size will become zero
  frequently, only not if there are temporary buildd power issues
  The graph at [1] illustrates this nicely, you can see that for example
  somewhere around 15 feb 2005 all architecture's Needs-Build queue was
  zero, and that only s390, mipsel and arm have not reached zero for the
  last few days
- if Needs-Build is zero, all packages that are in this state are build,
  including package zzzzz from x11-extra. As long as the queue does
  reach zero from time to time, there is no starvation.

If the queue is non-zero for a longer time, there is a problem in buildd
machine power, and the wanna-build admin has choosen to in this case
allocate the buildd power that remains to the building of packages that
are of higher priority, regardless of their age in the queue. The
allocation of a scarce resource is almost by definition a trade-off, and
this is the decision that has been made.


[1] http://people.debian.org/~igloo/needs-build-graph/index.php?days=30

Jeroen van Wolffelaar
Jeroen@wolffelaar.nl (also for Jabber & MSN; ICQ: 33944357)

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