linux-kernel - Re: [PATCH 07/13] mm: meminit: Initialise a subset of struct pages if CONFIG_DEFERRED_STRUCT_PAGE

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Date:	Tue, 28 Apr 2015 10:53:23 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Linux-MM <linux-mm@...ck.org>, Nathan Zimmer <nzimmer@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Waiman Long <waiman.long@...com>,
	Scott Norton <scott.norton@...com>,
	Daniel J Blueman <daniel@...ascale.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/13] mm: meminit: Initialise a subset of struct pages
 if CONFIG_DEFERRED_STRUCT_PAGE_INIT is set

On Mon, Apr 27, 2015 at 03:43:44PM -0700, Andrew Morton wrote:
> On Thu, 23 Apr 2015 11:33:10 +0100 Mel Gorman <mgorman@...e.de> wrote:
> 
> > This patch initalises all low memory struct pages and 2G of the highest zone
> > on each node during memory initialisation if CONFIG_DEFERRED_STRUCT_PAGE_INIT
> > is set. That config option cannot be set but will be available in a later
> > patch.  Parallel initialisation of struct page depends on some features
> > from memory hotplug and it is necessary to alter alter section annotations.
> > 
> >  ...
> >
> > +#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> > +#define __defermem_init __meminit
> > +#define __defer_init    __meminit
> > +#else
> > +#define __defermem_init
> > +#define __defer_init __init
> > +#endif
> 
> Could we get some comments describing these?  What they do, when and
> where they should be used.  I have a suspicion that the naming isn't
> good, but I didn't spend a lot of time reverse-engineering the
> intent...
> 

Of course. The next version will have

+/*
+ * Deferred struct page initialisation requires some early init functions that
+ * are removed before kswapd is up and running. The feature depends on memory
+ * hotplug so put the data and code required by deferred initialisation into 
+ * the __meminit section where they are preserved.
+ */

-- 
Mel Gorman
SUSE Labs
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