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

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Date:   Thu, 3 May 2018 15:39:49 -0700
From:   "prakash.sangappa" <prakash.sangappa@...cle.com>
To:     Christopher Lameter <cl@...ux.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 05/03/2018 11:03 AM, Christopher Lameter wrote:
> On Tue, 1 May 2018, Prakash Sangappa wrote:
>
>> For analysis purpose it is useful to have numa node information
>> corresponding mapped address ranges of the process. Currently
>> /proc/<pid>/numa_maps provides list of numa nodes from where pages are
>> allocated per VMA of the process. This is not useful if an user needs to
>> determine which numa node the mapped pages are allocated from for a
>> particular address range. It would have helped if the numa node information
>> presented in /proc/<pid>/numa_maps was broken down by VA ranges showing the
>> 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.

>> 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.