[LTP] [PATCH 0/3] cpuset_regression_test: convert and improve

[Joerg Vehlow]

Hi,

this is more or less a v2 of a patch I send previously (patch 3).
I know that richard is not entirely happy with this patch, I will
give it another try anyway...
It is either this patch or another patch, that has to look through
the cgroup hierarchy, to check if there is any group,that explicitely
uses cpu 0. 

To me, it is a better solution to just change groups for a short time,
and check if the bug exists. If ltp tests are running, the chance, that
there is anything running, that really needs a correct cpuset is very low.
I am comming from a system, where cgroups are setup by a container launcher,
that just happens to assign cpus to the containers - not even exclusively.
LTP tests are used as some part of the testsuite, to test as close to a
production system as possible.

The only way I could think of a process misbehaving by disabeling cpu pinning,
would be a badly written multithread application, that cannot correctly run,
if threads are really running in parallel, but this would also require a scheduling
policy, that makes scheduling points predicatable. While I know that software like
that exists (in fact I was working on something like that in the past), I think it
is highly unlikely, that it is running parallel to ltp.
And even then, this could be mitigated by not just setting cpu binding to undefined,
but to one fixed core. But with the changes in patch 2, this is not possible.

But anyhow ltp fiddles with lots of critical system parameters during it's runtime,
there is no guarantee, that an application that requires some very specific kernel
runtime settings survives this. That's why I would still vote for this patch.

Jörg