Messages in this thread | | | Subject | Re: [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node information | From | Prakash Sangappa <> | Date | Thu, 10 May 2018 09:00:24 -0700 |
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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/<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. >>> 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 >
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