[Swift-devel] Expected behavior for scheduler slow-start with coasters?

[Ben Clifford]

> Is there a simpler, alternate scheduler algorithm that you could plug in as a
> global, settable alternative to the current one when all sites are using
> coasters?

You can set the initialScore profile key very high[1] so that Swift will 
starts at full load rather than low load. This is basically "the simpler, 
alterative scheduler algorithm" that you are looking for.

You will however runinto a different manifestation of the same problem 
that coastersPerNode does not work properly and will likely attempt to 
massively overallocate workers.

Its not a bug in the scheduler - its a bug in the implementation of 
coastersPerNode that causes it to attempt to allocate one node per excess 
job.

In the longer term, as Mihael said, the interface between the scheduler 
and execution systems needs to change because coasters don't fit in the 
present abstraction very well.

[1] (to about 100 - the actual formula is rather opaque and I have to 
rederive it every time because I never write it down)

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