linux-kernel - Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent

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Date:   Fri, 16 Feb 2018 09:41:36 -0600 (CST)
From:   Christopher Lameter <cl@...ux.com>
To:     Matthew Wilcox <willy@...radead.org>
cc:     Michal Hocko <mhocko@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org
Subject: Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore
 for percent

On Thu, 15 Feb 2018, Matthew Wilcox wrote:

> On Thu, Feb 15, 2018 at 09:49:00AM -0600, Christopher Lameter wrote:
> > On Thu, 15 Feb 2018, Matthew Wilcox wrote:
> >
> > > What if ... on startup, slab allocated a MAX_ORDER page for itself.
> > > It would then satisfy its own page allocation requests from this giant
> > > page.  If we start to run low on memory in the rest of the system, slab
> > > can be induced to return some of it via its shrinker.  If slab runs low
> > > on memory, it tries to allocate another MAX_ORDER page for itself.
> >
> > The inducing of releasing memory back is not there but you can run SLUB
> > with MAX_ORDER allocations by passing "slab_min_order=9" or so on bootup.
>
> Maybe we should try this patch in order to automatically scale the slub
> page size with the amount of memory in the machine?

Well setting slub_min_order may cause allocation failures. You would leave
that at 0 for a prod configuration. Setting slub_max_order higher would
work.