linux-kernel - Re: [RFC PATCH] mm: thp: Add per-mm

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Date:	Mon, 13 Jan 2014 12:59:44 -0600
From:	Alex Thorlton <athorlton@....com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Rik van Riel <riel@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Al Viro <viro@...iv.linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] mm: thp: Add per-mm_struct flag to control THP

On Sun, Jan 12, 2014 at 02:56:00PM +0100, Oleg Nesterov wrote:
> On 01/11, Alex Thorlton wrote:
> >
> > On Sat, Jan 11, 2014 at 04:53:37PM +0100, Oleg Nesterov wrote:
> >
> > > I simply can't understand, this all looks like overkill. Can't you simply add
> > >
> > > 	#idfef CONFIG_TRANSPARENT_HUGEPAGE
> > > 	case GET:
> > > 		error = test_bit(MMF_THP_DISABLE);
> > > 		break;
> > > 	case PUT:
> > > 		if (arg2)
> > > 			set_bit();
> > > 		else
> > > 			clear_bit();
> > > 		break;
> > > 	#endif
> > >
> > > into sys_prctl() ?	
> >
> > That's probably a better solution.  I wasn't sure whether or not it was
> > better to have two functions to handle this, or to have one function
> > handle both.  If you think it's better to just handle both with one,
> > that's easy enough to change.
> 
> Personally I think sys_prctl() can handle this itself, without a helper.
> But of course I won't argue, this is up to you.
> 
> My only point is, the kernel is already huge ;) Imho it makes sense to
> try to lessen the code size, when the logic is simple.

I agree with you here as well.  There was a mixed bag of PRCTLs using
helpers vs. ones that put the code right into sys_prctl.  I just
arbitrarily chose to use a helper here.  I'll switch that over for v2.

- Alex
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