Message-ID: <4377031F.5000902@bigpond.net.au>
Date: Sun, 13 Nov 2005 20:10:55 +1100
From: Peter Williams <pwil3058@bigpond.net.au>
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To: Con Kolivas <kernel@kolivas.org>
CC: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Chris Han <xiphux@gmail.com>,
       William Lee Irwin III <wli@holomorphy.com>,
       Jake Moilanen <moilanen@austin.ibm.com>
Subject: Re: [PATCH] plugsched - update Kconfig-1
References: <434F01EA.6060709@bigpond.net.au> <200511131244.48358.kernel@kolivas.org> <4376CD9F.6040309@bigpond.net.au> <200511131637.40704.kernel@kolivas.org>
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Con Kolivas wrote:
> On Sun, 13 Nov 2005 16:22, Peter Williams wrote:
> 
>>Con Kolivas wrote:
>>
>>>On Sun, 13 Nov 2005 12:34, Peter Williams wrote:
>>>
>>>>1. Make the ability to select which schedulers are built in independent
>>>>of EMBEDDED.
>>>>2. Only offer builtin schedulers as choice for the default scheduler.
>>>>3. Only build in ingosched if PLUGSCHED is not configured.
>>>
>>>I disagree with 3. Surely people might want to build in only one
>>>scheduler that is not ingosched without other choices.
>>
>>Yes, and they would be able to do that by selecting PLUGSCHED and then
>>selecting only the scheduler that they want.  But this then leads to the
>>observation that PLUGSCHED is probably makes things unnecessarily
>>complex and all that is required is a means to select the schedulers to
>>be built in and a choice of default (much like for the IO schedulers)?
> 
> 
> Indeed it may be better to remove the "plugsched" option entirely. Once 
> patched in it's not like you are building the kernel without the plugsched 
> infrastructure. Provided each extra scheduler does not increase the kernel 
> size too much (and a test build with/without all schedulers should tell you 
> that), it may be best to just have the scheduler choice in the top menu and 
> only expose the "schedulers to build in" under embedded. 

I can't see why this should be restricted to embedded systems?

> 
> Of course if adding all the schedulers adds a lot of size to the kernel then 
> it would be best to retain the "build support for multiple cpu schedulers" 
> and default it to off.

You achieve the same just by selecting only one scheduler.  PLUGSCHED 
(currently) doesn't directly control the inclusion of any code and it's 
only effect is by controlling which schedulers are included.  It may be 
possible to change this so that the checking of the boot time scheduler 
selection code is excluded.

> Do you have a quick comparison of build sizes 
> with/without the various cpu schedulers?

I'll check. I'll also see how much difference the boot time selection 
code adds but I doubt whether it's very much.

> Last time I checked, staircase was a 
> few hundred bytes larger than mainline despite being 200 lines of code less, 
> probably due to its largely inline nature.

Each scheduler costs about 10kB on average.  Mine are the largest :-( 
(too many features including making extra stats available via /proc?) 
and I should look at improving that.

Peter
-- 
Peter Williams                                   pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce
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