linux-kernel - Re: [PATCH] mm/page_alloc: Clean up check_for

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Date:   Wed, 29 Aug 2018 22:34:32 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     mhocko@...e.com, vbabka@...e.cz, Pavel.Tatashin@...rosoft.com,
        sfr@...b.auug.org.au, iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Oscar Salvador <osalvador@...e.de>,
        Lai Jiangshan <laijs@...fujitsu.com>
Subject: Re: [PATCH] mm/page_alloc: Clean up check_for_memory

On Tue, Aug 28, 2018 at 02:35:30PM -0700, Andrew Morton wrote:
> > First, we should only set N_HIGH_MEMORY in case we have
> > CONFIG_HIGHMEM.
> 
> Why?  Just a teeny optimization?

Hi Andrew,

Optimization was not really my point here, my point was to make
the code less subtle and more clear.
One may wonder why we set N_HIGH_MEMORY unconditionally when
__only__ CONFIG_HIGHMEM matters for this case, and why we set 
N_NORMAL_MEMORY __only__ for CONFIG_HIGHMEM when we should not care
about that at all.

I do not really expect a big impact here, mainly because check_for_memory
is only being used during boot.

-- 
Oscar Salvador
SUSE L3