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

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Date:   Fri, 4 May 2018 09:27:04 -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 5/4/18 7:57 AM, Christopher Lameter wrote:
> 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?

Currently 'numa_maps' gives a list of numa nodes, memory is allocated per
VMA.
Ex. we get something like from numa_maps.

04000  N0=1,N2=2 kernelpagesize_KB=4

First is the start address of a VMA. This VMA could be much larger then 
3 4k pages.
It does not say which address in the VMA has the pages mapped.

>
>>>> 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.
>