linux-kernel - Re: [RFC PATCH 00/16] 1GB THP support on x86

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Message-ID: <7ed82cb06074b30c2956638082c515fb179f69a3.camel@surriel.com>
Date:   Tue, 08 Sep 2020 10:41:10 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Michal Hocko <mhocko@...e.com>, Zi Yan <ziy@...dia.com>
Cc:     David Hildenbrand <david@...hat.com>, Roman Gushchin <guro@...com>,
        "Kirill A. Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        David Nellans <dnellans@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 00/16] 1GB THP support on x86_64

On Tue, 2020-09-08 at 16:35 +0200, Michal Hocko wrote:

> A global knob is insufficient. 1G pages will become a very precious
> resource as it requires a pre-allocation (reservation). So it really
> has
> to be an opt-in and the question is whether there is also some sort
> of
> access control needed.

The 1GB pages do not require that much in the way of
pre-allocation. The memory can be obtained through CMA,
which means it can be used for movable 4kB and 2MB
allocations when not
being used for 1GB pages.

That makes it relatively easy to set aside
some fraction
of system memory in every system for 1GB and movable
allocations, and use it for whatever way it is needed
depending on what workload(s) end up running on a system.

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