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

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Message-ID: <20161207164554.b73qjfxy2w3h3ycr@techsingularity.net>
Date:   Wed, 7 Dec 2016 16:45:54 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Christoph Lameter <cl@...ux.com>
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, Dec 07, 2016 at 10:40:47AM -0600, Christoph Lameter wrote:
> On Wed, 7 Dec 2016, Mel Gorman wrote:
> 
> > Which is related to the fundamentals of fragmentation control in
> > general. At some point there will have to be a revisit to get back to
> > the type of reliability that existed in 3.0-era without the massive
> > overhead it incurred. As stated before, I agree it's important but
> > outside the scope of this patch.
> 
> What reliability issues are there? 3.X kernels were better in what
> way? Which overhead are we talking about?
> 

3.0-era kernels had better fragmentation control, higher success rates at
allocation etc. I vaguely recall that it had fewer sources of high-order
allocations but I don't remember specifics and part of that could be the
lack of THP at the time. The overhead was massive due to massive stalls
and excessive reclaim -- hours to complete some high-allocation stress
tests even if the success rate was high.

-- 
Mel Gorman
SUSE Labs