Re: Userspace scheduler?

To: <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: Userspace scheduler?
From: Wensong Zhang <wensong@xxxxxxxxxxxx>
Date: Thu, 6 Dec 2001 22:41:06 +0800 (CST)
On Thu, 6 Dec 2001, Alexandre CASSEN wrote:

> Hi,
> >> What policy the user space can propose? Examples?
> >
> >In this case, it is a rather complex load balancing decision based on
> constant
> >feedback from the next tier fed through a neural network and then chosing
> the
> >best server.
> >
> >(You may shot me now; this wasn't my idea, I am just pondering how to
> >integrate this with LVS)
> Interresting,... I am currently working on an algorithm to change the
> realserver pool weigth according to realserver response time... What kind
> of algorithm are you using in your neural network ? A neural network can be
> used to manipulate realservers weight and that way increase the cluster
> response time.

I uses the following algorithm in the piranha code,

        weight <- weight + A * pow(1-load, 1/3)        when load!=1
        where A is the scale of weight adjustment, load is server loadavg

        weight is not changed, when load is 1.

It was addded probably two years ago, I don't remember exactly.

It might be better to replace the load variable with the aggregate_load,

        weight <- weight + A * pow(1-aggregate_load, 1/3)

        aggregate_load = R1*LOADAVG + R2*RESPONSE + R3*DISK + ...
        where the sum of Ri is 1, and these variables (LOADAVG,RESPONSE..)
        should be normalized into an interval (such as [0,8])
        aggregate_load > 1 means that server is overloaded.
        aggregate_load < 1 means that server is under loaded.

The parameter Ri can give users opportunity to adapt to their
applications, such as CPU-intensive, or IO-intensive applications.

Just a small suggestion.



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