linux-kernel - Re: Comments on UV tlb flushing

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Message-ID: <20080729200455.GA20559@sgi.com>
Date:	Tue, 29 Jul 2008 15:04:55 -0500
From:	Cliff Wickman <cpw@....com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>, steiner@....com,
	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: Comments on UV tlb flushing

On Tue, Jul 29, 2008 at 10:46:41AM -0700, Jeremy Fitzhardinge wrote:
> Cliff Wickman wrote:
>> But if the tlb_uv.o code should be present in "every" distro x86 kernel
>> I don't see the point of having to configure it in.  Why not just
>> configure it out for small (embedded) kernels?
>
> Because it's not an binary thing.  Lots of people who are compiling  
> their own kernels for specialized uses don't set CONFIG_EMBEDDED, but  
> also don't want a kitchen sink kernel.  6k isn't that much, but if every  
> obscure platform enabled some always-on code it rapidly starts to build 
> up.

But UV will not be obscure! It will be common among x86_64 :)  
I know what you're talking about.  It may sometimes be useful to turn
off chunks of code you don't need. 
But is the specialized application of 64-bit processors big enough to
warrant the feature?
The size of most any 64-bit system would, I would think, make 6k of
code insignificant.
And the more options you add, the more likely someone will pick
combinations that won't work together.

> Basically, if you want to make sure if you're going to get some level of  
> distro support, you need to make contact with the distros directly and  
> talk about what you'd like them to do.
>    J
And we do. And could reasonably expect that they would turn on that
option for x86_64 kernels.  We'd just, of course, rather not have to watch
and prompt to be sure all x86_64 kernels will run on our hardware.

-Cliff
-- 
Cliff Wickman
Silicon Graphics, Inc.
cpw@....com
(651) 683-3824
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