linux-kernel - Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v7

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Message-ID: <alpine.DEB.2.20.1612070849260.8398@east.gentwo.org>
Date:   Wed, 7 Dec 2016 08:52:27 -0600 (CST)
From:   Christoph Lameter <cl@...ux.com>
To:     Mel Gorman <mgorman@...hsingularity.net>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v7

On Wed, 7 Dec 2016, Mel Gorman wrote:

> SLUB has been the default small kernel object allocator for quite some time
> but it is not universally used due to performance concerns and a reliance
> on high-order pages. The high-order concerns has two major components --

SLUB does not rely on high order pages. It falls back to lower order if
the higher orders are not available. Its a performance concern.

This is also an issue for various other kernel subsystems that really
would like to have larger contiguous memory area. We are often seeing
performance constraints due to the high number of 4k segments when doing
large scale block I/O f.e.

Otherwise I really like what I am seeing here.