From: Michal Hocko <mhocko@kernel.org>
To: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Christopher Lameter <cl@linux.com>,
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
Subject: Re: [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node information
Date: Fri, 11 May 2018 08:39:52 +0200 [thread overview]
Message-ID: <20180511063952.GA23231@dhcp22.suse.cz> (raw)
In-Reply-To: <ce2c36aa-8c03-63d6-e1ce-031197f45a5d@oracle.com>
On Thu 10-05-18 09:00:24, Prakash Sangappa wrote:
>
>
> 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?
absolutely. We do check ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)
to make sure the access is authorised.
>
> 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?
No, see PTRACE_MODE_READ_REALCREDS check in move_pages.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-05-11 6:39 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-02 5:58 [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node information Prakash Sangappa
2018-05-02 21:33 ` Andrew Morton
2018-05-02 22:28 ` Dave Hansen
2018-05-02 23:17 ` prakash.sangappa
2018-05-03 8:46 ` Anshuman Khandual
2018-05-03 22:27 ` prakash.sangappa
2018-05-03 22:26 ` Dave Hansen
2018-05-07 23:22 ` prakash.sangappa
2018-05-08 0:05 ` Dave Hansen
2018-05-08 1:16 ` prakash.sangappa
2018-05-09 23:31 ` Dave Hansen
2018-09-12 20:42 ` prakash.sangappa
2018-09-12 20:57 ` prakash.sangappa
2018-09-14 1:33 ` Jann Horn
2018-09-14 6:21 ` Michal Hocko
2018-09-14 12:49 ` Jann Horn
2018-09-14 13:49 ` Michal Hocko
2018-09-14 18:07 ` Prakash Sangappa
2018-09-14 18:14 ` Jann Horn
2018-05-02 23:43 ` prakash.sangappa
2018-05-03 8:57 ` Michal Hocko
2018-05-03 22:37 ` prakash.sangappa
2018-05-04 11:10 ` Michal Hocko
2018-05-03 18:03 ` Christopher Lameter
2018-05-03 22:39 ` prakash.sangappa
2018-05-04 11:12 ` Michal Hocko
2018-05-04 16:18 ` Prakash Sangappa
2018-05-10 7:42 ` Michal Hocko
2018-05-10 16:00 ` Prakash Sangappa
2018-05-11 6:39 ` Michal Hocko [this message]
2018-05-04 14:57 ` Christopher Lameter
2018-05-04 16:27 ` Prakash Sangappa
2018-05-07 14:47 ` Christopher Lameter
2018-05-07 22:50 ` prakash.sangappa
2018-05-08 12:53 ` Christopher Lameter
2018-09-12 23:02 Alexey Dobriyan
2018-09-13 22:17 ` prakash.sangappa
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