Message-Id: <5.2.1.1.2.20060108054203.00bf38c0@pop.gmx.net>
Date: Sun, 08 Jan 2006 06:51:24 +0100
To: Peter Williams <pwil3058@bigpond.net.au>
From: Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH] sched: Fix adverse effects of NFS client     
  on	interactive response
Cc: Helge Hafting <helgehaf@aitel.hist.no>,
       Trond Myklebust <trond.myklebust@fys.uio.no>,
       Ingo Molnar <mingo@elte.hu>, Con Kolivas <kernel@kolivas.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
In-Reply-To: <43C0517E.8020604@bigpond.net.au>
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At 10:40 AM 1/8/2006 +1100, Peter Williams wrote:
>Mike Galbraith wrote:
>>>   One slight variation of your scheme would be to measure the average 
>>> length of the CPU runs that the task does (i.e. how long it runs 
>>> without voluntarily relinquishing the CPU) and not allowing them to 
>>> defer the shift to the expired array if this average run length is 
>>> greater than some specified value.  The length of this average for each 
>>> task shouldn't change with system load.  (This is more or less saying 
>>> that it's ok for a task to stay on the active array provided it's 
>>> unlikely to delay the switch between the active and expired arrays for 
>>> very long.)
>>
>>Average burn time would indeed probably be a better metric, but that 
>>would require doing bookkeeping is the fast path.
>
>Most of the infrastructure is already there and the cost of doing the 
>extra bits required to get this metric would be extremely small.  The 
>hardest bit would be deciding on the "limit" to be applied when deciding 
>whether to let a supposed interactive task stay on the active array.

Yeah, I noticed run_time when I started implementing my first cut.  (which 
is of course buggy)


>By the way, it seems you have your own scheduler versions?  If so are you 
>interested in adding them to the collection in PlugSched?

No, I used to do a bunch of experimentation in fairness vs interactivity, 
but they all ended up just trading one weakness for an other.

         -Mike 

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