From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prakash Sangappa Subject: Re: [RFC PATCH] Add /proc//numa_vamaps for numa node information Date: Thu, 10 May 2018 09:00:24 -0700 Message-ID: References: <1525240686-13335-1-git-send-email-prakash.sangappa@oracle.com> <20180504111211.GO4535@dhcp22.suse.cz> <20180510074254.GE32366@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20180510074254.GE32366@dhcp22.suse.cz> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Michal Hocko Cc: Christopher Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, drepper@gmail.com, rientjes@google.com List-Id: linux-api@vger.kernel.org On 5/10/18 12:42 AM, Michal Hocko wrote: > On Fri 04-05-18 09:18:11, Prakash Sangappa wrote: >> >> On 5/4/18 4:12 AM, Michal Hocko wrote: >>> On Thu 03-05-18 15:39:49, prakash.sangappa wrote: >>>> 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//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//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. >>> yes we have. See move_pages... >> Sure using move_pages, not based on just 'numa_maps'. >> >>>>>> 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. >>> Well, that breaks the layout randomization, doesn't it? >> Exposing numa node information itself should not break randomization right? > I thought you planned to expose address ranges for each numa node as > well. /me confused. Yes, are you suggesting this information should not be available to a regular user? Is it not possible to get that same information using the move_pages() api as a regular user, although one / set of pages at a time? >> It would be upto the application. In case of randomization, the application >> could generate  address range traces of interest for debugging and then >> using numa node information one could determine where the memory is laid >> out for analysis. > ... even more confused >