-------- Original Message  --------
Subject: Re:[zones-discuss] zones and cpu shares
From: Jeff Victor <[EMAIL PROTECTED]>
Cc: Niklas Jonsson <[EMAIL PROTECTED]>, zones-discuss@opensolaris.org
Date: Thu Jul 19 2007 16:23:13 GMT+0200 (CEST)

> Renaud Manus wrote:
>> With cpu-shares, resources are shared but you're not guaranteed that a 
>> zone gets a minimum of 50% cpu share available *all* the time.
> Are you referring to the fact that a zone with one-half of the shares in its 
> pool would not receive 50% of the CPU power in that pool over an arbitrarily 
> short period of time, e.g. 1 millisecond?  Or are you referring to something 
> else?

I'm referring to the way FSS(7) works:

      While FSS is designed  to  fairly  allocate  cycles  over  a
      long-term time period, it is possible that projects will not
      receive their allocated shares worth of CPU  cycles  due  to
      uneven  demand.  This makes one-shot, instantaneous analysis
      of FSS performance data unreliable.

      Note that share is not the same as  utilization.  A  project
      may be allocated 50% of the system, although on the average,
      it uses just 20%. Shares serve to cap a project's CPU  usage
      only  when  there is competition from other projects running
      on the same processor set. When  there  is  no  competition,
      utilization  may be larger than entitlement based on shares.

-- Renaud

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