[torquedev] [Bug 195] cpuset VFS path change for 3.x kernels

bugzilla-daemon at supercluster.org bugzilla-daemon at supercluster.org
Thu May 24 21:48:57 MDT 2012


http://www.clusterresources.com/bugzilla/show_bug.cgi?id=195

--- Comment #5 from Chris Samuel <chris at csamuel.org> 2012-05-24 21:48:57 MDT ---
(In reply to comment #4)

> I do not use noprefix option, thus ls shows "cpuset." prefixes.

Neither do I, and it ls does not show "cpuset." prefixes.  The reason is that
you already have a cgroup filesystem mounted and I do not.

This change in behaviour is since the Linux kernel commit
f9ab5b5b0f5be506640321d710b0acd3dca6154a "cgroups: forbid noprefix if mounting
more than just cpuset subsystem".

I'll try and find some time to report this as a kernel regression to see what
their attitude to this is - to me it seems like the sort of ABI behaviour
change and consequent user space breakage that Linus hates.

> There is no such thing as a stable kernel API and there are good reasons for
> this.

You are mistaking the *internal* kernel APIs (which are indeed unstable for
very good reason) with the external kernel ABIs exposed to user space and which
have different rules applied.

There has been an attempt to document the level of stability of interfaces in
Documentation/ABI directory (see the README for Greg-KH's reasoning), but as
far as I can tell the cpuset/cgroup stuff has not been added yet.

> New applications will eventually use modern way of handling things, so
> torque should adapt as well otherwise conflicts will occur sooner or later.

Agreed, but Torque will need to know to cope with both cases dynamically.

> Anyway if you plan to stick to old file names at least for a while, please put
> somewhere in the documentation, that people should use -o noprefix.

Sounds like a good idea, I've just tested that on a RHEL5 system and it didn't
complain about not knowing what that meant.

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