linux-kernel - Re: [PATCH] make GFP_NOTRACK flag unconditional

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Message-ID: <0000013a0dbfc498-6debffd5-cd68-404c-92a4-4f88d40cf41b-000000@email.amazonses.com>
Date:	Fri, 28 Sep 2012 16:40:02 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Glauber Costa <glommer@...allels.com>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH] make GFP_NOTRACK flag unconditional

On Fri, 28 Sep 2012, Glauber Costa wrote:

> On 09/28/2012 06:28 PM, Christoph Lameter wrote:
> > On Fri, 28 Sep 2012, Glauber Costa wrote:
> >
> >> There was a general sentiment in a recent discussion (See
> >> https://lkml.org/lkml/2012/9/18/258) that the __GFP flags should be
> >> defined unconditionally. Currently, the only offender is GFP_NOTRACK,
> >> which is conditional to KMEMCHECK.
> >>
> >> This simple patch makes it unconditional.
> >
> > __GFP_NOTRACK is only used in context where CONFIG_KMEMCHECK is defined?
> >
> > If that is not the case then you need to define GFP_NOTRACK and substitute
> > it where necessary.
> >
>
> The flag is passed around extensively, but I was imagining the whole
> point of that is that having the flag itself is harmless, and will be
> ignored by the page allocator ?

Looking through it shows almost nothing that is affected.

One thing though is that defining __GFP_NOTRACK to 0 eliminates an "or"
operation in alloc_slab_page().

That is already on the slob path so I guess that is minimal

Acked-by: Christoph Lameter <cl@...ux.com>

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