linux-kernel - Re: [RFC PATCH] Add /proc/<pid>/numa

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Message-ID: <alpine.DEB.2.21.1805040955550.10847@nuc-kabylake>
Date:   Fri, 4 May 2018 09:57:54 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     "prakash.sangappa" <prakash.sangappa@...cle.com>
cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-api@...r.kernel.org, akpm@...ux-foundation.org,
        mhocko@...e.com, kirill.shutemov@...ux.intel.com,
        n-horiguchi@...jp.nec.com, drepper@...il.com, rientjes@...gle.com
Subject: Re: [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node
 information

On Thu, 3 May 2018, prakash.sangappa wrote:

> > > exact numa node from where the pages have been allocated.
> > Cant you write a small script that scans the information in numa_maps and
> > then displays the total pages per NUMA node and then a list of which
> > ranges have how many pages on a particular node?
>
> Don't think we can determine which numa node a given user process
> address range has pages from, based on the existing 'numa_maps' file.

Well the information is contained in numa_maps I thought. What is missing?

> > > reading this file will not be restricted(i.e requiring CAP_SYS_ADMIN).
> > So a prime motivator here is security restricted access to numa_maps?
> No it is the opposite. A regular user should be able to determine
> numa node information.

That used to be the case until changes were made to the permissions for
reading numa_maps.