[lkml]   [2020]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH -tip 26/32] sched: Add a second-level tag for nested CGroup usecase
On Tue, Dec 01, 2020 at 10:18:00PM -0800, Josh Don wrote:
> Hey Peter,
> On Wed, Nov 25, 2020 at 5:43 AM Peter Zijlstra <> wrote:
> >
> > Why can't the above work by setting 'tag' (that's a terrible name, why
> > does that still live) in CDE? Have the most specific tag live. Same with
> > that thread stuff.
> The motivation is to allow an unprivileged user the ability to
> configure the trust hierarchy in a way that otherwise wouldn't be
> possible for a given cgroup hierarchy. For example given a cookie'd
> hierarchy such as:
> A
> / | | \
> B C D E
> the user might only want subsets of {B, C, D, E} to share. For
> instance, the user might only want {B,C} and {D, E} to share. One way
> to solve this would be to allow the user to write the group cookie
> directly. However, this interface would need to be restricted to
> privileged users, since otherwise the cookie could be configured to
> share with any arbitrary cgroup. The purpose of the 'color' field is
> to expose a portion of the cookie that can be modified by a
> non-privileged user in order to achieve this sharing goal.
> If this doesn't seem like a useful case, I'm happy to drop this patch
> from the series to unblock it.

Well, the traditional cgroup way of doing that would be to:

/ \
T1 T2
/ \

And tag T1 if you want B,C to share.

So me the color thing reads like an end-run around the cgroup hierarchy.

 \ /
  Last update: 2020-12-02 09:05    [W:0.351 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site