Chatted with BenM offline on this. There's another option what both of us
agreed that it's probably better than any of the ones mentioned above.
The idea is to make `allocable` return the portion of the input resources
that are allocatable, and strip the unelectable portion.
For example:
1) If the input resources are "cpus:0.001,gpus:1", the `allocatable` method
will return "gpus:1".
2) If the input resources are "cpus:1,mem:1", the `allocatable` method will
return "cpus:1".
3) If the input resources are "cpus:0.001,mem:1", the `allocatable` method
will return an empty Resources object.
Basically, the algorithm is like the following:
allocatable = input
foreach known resource type t: do
r = resources of type t from the input
if r is less than the min resource of type t; then
allocatable -= r
fi
done
return allocatable
Let me know what do you guys think!
Thanks!
- Jie
On Fri, Mar 2, 2018 at 4:44 PM, Benjamin Mahler <[email protected]> wrote:
> I think (2) would need to be:
>
> bool HierarchicalAllocatorProcess::allocatable(
> const Resources& resources)
> {
> if (something outside {cpu, mem, disk} is present) return true
> else return true iff at least one of {cpu, mem, disk} has >= {MIN_CPU,
> MIN_MEM, MIN_DISK}
> }
>
> Otherwise, 1 GPU would be offered but 1GPU + 0.001 CPU would not?
>
> On Fri, Mar 2, 2018 at 9:27 AM, Jie Yu <[email protected]> wrote:
>
> > Hi,
> >
> > The allocatable
> > <https://github.com/apache/mesos/blob/1.5.x/src/master/alloc
> > ator/mesos/hierarchical.cpp#L2471-L2479>
> > check in the allocator (shown below) was originally introduced to help
> > alleviate the situation where a framework receives some resources, but no
> > cpu/memory, thus cannot launch a task.
> >
> > bool HierarchicalAllocatorProcess::allocatable(
> > const Resources& resources)
> > {
> > Option<double> cpus = resources.cpus();
> > Option<Bytes> mem = resources.mem();
> >
> > return (cpus.isSome() && cpus.get() >= MIN_CPUS) ||
> > (mem.isSome() && mem.get() >= MIN_MEM);
> > }
> >
> > As pointed by Benjamin in MESOS-7398
> > <https://issues.apache.org/jira/browse/MESOS-7398>, it now seems to
> mainly
> > help to minimize the performance overhead from too many small offers
> > (instead too small resource amounts are kept out of the offer pool until
> > they became accumulated into larger resources).
> >
> > This check does cause issues when new resources types are introduced. For
> > instance, this check does prevent GPU resources alone from being
> allocated
> > to a framework. There are some other issues we discover MESOS-8626
> > <https://issues.apache.org/jira/browse/MESOS-8626>.
> >
> > There are several proposals:
> >
> > (1) *Completely remove this check*. This check is a heuristic anyway, and
> > only applies to a subset of resources (cpu/memory). However, there might
> be
> > some implication of that change since it's also leveraged to prevent too
> > many small offers. *If you are concerned about this approach, please
> raise
> > your voice.*
> >
> > (2) *Consider adjust the check to the following. *
> >
> > bool HierarchicalAllocatorProcess::allocatable(
> > const Resources& resources)
> > {
> > Option<double> cpus = resources.cpus();
> > Option<Bytes> mem = resources.mem();
> >
> > if (cpus.isSome() && mem.isSome()) {
> > return cpus.get() >= MIN_CPUS || mem.get() >= MIN_MEM;
> > } else if (cpus.isSome()) {
> > return cpus.get() >= MIN_CPUS;
> > } else if (mem.isSome()) {
> > return mem.get() >= MIN_MEM;
> > } else {
> > return true;
> > }
> > }
> >
> > Let me know what you think! Thanks!
> >
> > - Jie
> >
>
