Hi, Daniel,

On Wed, Mar 17, 2021 at 08:49:03AM +0100, Daniel Wagner wrote:

On Tue, Mar 16, 2021 at 04:07:05PM -0400, Peter Xu wrote:

quoted

I think what I'm missing is why we had such a restriction.  Quotting from the
commit ID:

IIRC, the current behavior allows the process to be placed into a cgroup
with a subset of CPUs and you just can do 'cyclictest -a -t'. Process
should not ignore external configuration. That's my whole point here.

In that case again I think a sane solution is not to check the cpu list in
every single tool we use, because even if we do that for all tools in rt-teets
repo, we can't guarantee to have this check for the rest tools to not ignore
this restriction.

A simple example is: what if the user specified "taskset -c $CPU cyclictest -a
$CPU -t 1 ..." where $CPU is not in the allowed list of current bash?  As long
as the taskset would work the so-called "environment" will be changed before
even loading cyclictest.

If you see that's the point I said we should fail at the same check point of
sched_setaffinity() rather than checking it explicitly in the tool, because
if we want a real-world restriction that's the only place I think it's possible..

But I'm not a cgroup/container guy, please correct me if I understood.

-- 
Peter Xu