linux-kernel - Re: [PATCH 8/8] mm: Remove __GFP

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Message-ID: <20171019143252.bviqsb7qxppzz32j@techsingularity.net>
Date:   Thu, 19 Oct 2017 15:32:52 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-FSDevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 8/8] mm: Remove __GFP_COLD

On Thu, Oct 19, 2017 at 03:42:12PM +0200, Vlastimil Babka wrote:
> From b002266c1a826805a50087db851f93e7a87ceb2f Mon Sep 17 00:00:00 2001
> From: Vlastimil Babka <vbabka@...e.cz>
> Date: Tue, 17 Oct 2017 16:03:02 +0200
> Subject: [PATCH] mm, page_alloc: simplify list handling in rmqueue_bulk()
> 
> The rmqueue_bulk() function fills an empty pcplist with pages from the free
> list. It tries to preserve increasing order by pfn to the caller, because it
> leads to better performance with some I/O controllers, as explained in
> e084b2d95e48 ("page-allocator: preserve PFN ordering when __GFP_COLD is set").
> 
> To preserve the order, it's sufficient to add pages to the tail of the list
> as they are retrieved. The current code instead adds to the head of the list,
> but then updates the list head pointer to the last added page, in each step.
> This does result in the same order, but is needlessly confusing and potentially
> wasteful, with no apparent benefit. This patch simplifies the code and adjusts
> comment accordingly.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Mel Gorman <mgorman@...hsingularity.net>

-- 
Mel Gorman
SUSE Labs