linux-kernel - Re: [PATCH 2/2] mm: page_alloc: High-order per-cpu page allocator v5

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Message-ID: <20161206135328.lvafbdemb3bjjktv@techsingularity.net>
Date:   Tue, 6 Dec 2016 13:53:28 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm: page_alloc: High-order per-cpu page allocator v5

On Tue, Dec 06, 2016 at 11:43:45AM +0900, Joonsoo Kim wrote:
> > actually clear at all it's an unfair situation, particularly given that the
> > vanilla code is also unfair -- the vanilla code can artifically preserve
> > MIGRATE_UNMOVABLE without any clear indication that it is a universal win.
> > The only deciding factor there was a fault-intensive workload would mask
> > overhead of the page allocator due to page zeroing cost which UNMOVABLE
> > allocations may or may not require. Even that is vague considering that
> > page-table allocations are zeroing even if many kernel allocations are not.
> 
> "Vanilla works like that" doesn't seem to be reasonable to justify
> this change.  Vanilla code works with three lists and it now become
> six lists and each list can have different size of page. We need to
> think that previous approach will also work fine with current one. I
> think that there is a problem although it's not permanent and would be
> minor. However, it's better to fix it when it is found.
> 

This is going in circles. I prototyped the modification which increases
the per-cpu structure slightly and will evaluate. It takes about a day
to run through the full set of tests. If it causes no harm, I'll release
another version.

-- 
Mel Gorman
SUSE Labs