-------- Original Message --------
Subject: Re:[zones-discuss] zones and cpu shares
From: Jeff Victor <[EMAIL PROTECTED]>
To: [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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