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Re: [Condor-users] negotiation algorithm with dynamic provisioning
- Date: Wed, 17 Nov 2010 11:25:09 -0700
- From: Jon May <jmay@xxxxxxx>
- Subject: Re: [Condor-users] negotiation algorithm with dynamic provisioning
My followup question was, essentially, "Is it possible to obtain different
behavior, such that a partitionable slot is fully utilized before other
partitionable slots are considered?" While I assume that optimal use of
resources is NP-hard, the current behavior is particularly nasty when jobs
requesting a wide variety of resources compete.
For example, the following scenario is rather common: Machines A and B each
have 8 cpus. User X has 8 jobs requiring 1 cpu. User Y has 1 job requiring 8
cpus. Assuming both users have equal priority, there's a 50/50 chance that Y
gets starved if X gets chosen first in the first negotiation cycle, and then
has one job assigned to A and one job assigned to B.
If I assume that there is no way to change the requirement that a
partionable slot can only match once per negotiation cycle, then I believe I
could achieve the behavior I wanted by making the following changes:
1) set ranks such that machines with the fewest resources have the highest
ranks (e.g. RANK = -Cpus)
2) allow at most one match per negotiation cycle. This essentially works
around the limitation above by ensuring all partitionable slots are always
in the resource list.
But is there any way to achieve the second change?
On 11/17/10 11:44 AM, "Erik Erlandson" <eerlands@xxxxxxxxxx> wrote:
>> I assume
>> that the resource list created at the beginning of negotiation comprises the
>> "real" slots, and when a match is made to a slot, a dynamic slot is created,
>> but the real slot is removed from the resource list. Thus, in a single
>> negotiation cycle, resources can only be taken from a single (real) slot at
>> most once.
> Hi Jon,
> Your understanding is correct: In a single negotiation cycle one job
> will match a partitionable slot. So, if a partitionable slot has (for
> example) 8 CPUs, it will take 8 negotiation cycles to fully utilize the
> partitionable slot. At this point, there will be the original slot, now
> showing 0 CPUs, and 8 dynamic slots.
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