linux-kernel - Re: [PATCH 1/2] mm, Make __get_user_pages return -EHWPOISON for HWPOISON page optionally

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Date:	Thu, 27 Jan 2011 17:12:44 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Huang Ying <ying.huang@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Dean Nelson <dnelson@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH 1/2] mm, Make __get_user_pages return -EHWPOISON for
 HWPOISON page optionally

On Fri, 28 Jan 2011 01:57:11 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> I personally would consider it cleaner to have clearly
> defined wrappers instead of complicted flags in the caller.
> 
> > The number of args to these functions is getting nutty - you'll
> > probably find that it is beneficial to inline these wrapepr functions, if
> > the number of callsites is small.
> 
> Really the functions are so heavy weight it should not matter.
> The problem with inlining is that you end up with the code in
> the header file and I personally find that much harder to browse
> instead of having everything in one file.

You'll cope.

> Also longer term we'll get compilers that can do cross-file inlining
> for optimized builds.

Which we'll probably need to turn off all over the place :(

> So please better avoid these kinds of micro optimizations unless
> it's a really really extremly speed critical path.

It's not just speed and it's not just .text size, either. Calling a
ten-arg function consumes stack space.
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