linux-kernel - Re: [PATCH] mm, oom: consider present pages for the node size

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Message-ID: <alpine.DEB.2.21.1908291519580.54347@chino.kir.corp.google.com>
Date:   Thu, 29 Aug 2019 15:20:16 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] mm, oom: consider present pages for the node size

On Thu, 29 Aug 2019, Michal Hocko wrote:

> From: Michal Hocko <mhocko@...e.com>
> 
> constrained_alloc calculates the size of the oom domain by using
> node_spanned_pages which is incorrect because this is the full range of
> the physical memory range that the numa node occupies rather than the
> memory that backs that range which is represented by node_present_pages.
> 
> Sparsely populated nodes (e.g. after memory hot remove or simply sparse
> due to memory layout) can have really a large difference between the
> two. This shouldn't really cause any real user observable problems
> because the oom calculates a ratio against totalpages and used memory
> cannot exceed present pages but it is confusing and wrong from code
> point of view.
> 
> Noticed-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Michal Hocko <mhocko@...e.com>

Acked-by: David Rientjes <rientjes@...gle.com>