linux-kernel - Re: [PATCH 08/24] net, diet: Make TCP metrics optional

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Message-ID: <20140614203326.GC3853@xo-6d-61-c0.localdomain>
Date:	Sat, 14 Jun 2014 22:33:26 +0200
From:	Pavel Machek <pavel@....cz>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Josh Triplett <josh@...htriplett.org>,
	David Miller <davem@...emloft.net>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, tom.zanussi@...ux.intel.com,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 08/24] net, diet: Make TCP metrics optional

On Tue 2014-05-06 11:33:11, Cong Wang wrote:
> On Tue, May 6, 2014 at 10:55 AM,  <josh@...htriplett.org> wrote:
> > On Tue, May 06, 2014 at 01:16:43PM -0400, David Miller wrote:
> >> From: josh@...htriplett.org
> >> Date: Tue, 6 May 2014 09:41:08 -0700
> >>
> >> > Every KB of RAM costs real money and SoC die area (for eDRAM/eSRAM).
> >>
> >> Another poster commented that 16MB of DRAM would be cheaper than
> >> the 2MB of ram you have on these boards, probably one that fits
> >> your size profile is available as well.
> >>
> >> 2MB is just a rediculous restriction.
> >
> > Embedded systems experts disagree with you there; there *are* systems
> > where the most cost-efficient approach is a few MB (or a few hundred KB)
> > of non-discrete memory.  We're not talking about socketed memory or even
> > soldered-down memory; we're talking about entire systems that fit on a
> > small SoC die.  The space not used by that extra RAM may well be better
> > spent on CPU optimizations, or some other integrated component.
> >
> > Such boards will be built, and many of them will run Linux, despite your
> > incredulity.  When you're building millions of a board, it's well worth
> > optimizing software to eliminate components from the bill of materials.
> 
> So why bothers 3.15+ Linux kernel? Why not use an old kernel e.g. 2.4.x?
> 2.4.x kernel doesn't have so many new features you want to get rid of here.

So.. what is kernel composed of? Ton of drivers and a bit of generic code.

And when doing this, you probably need the drivers from 3.x for your hardware.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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