[ Adding Dinakar to explicit cc list, since I mention his work.
Hopefully he can correct any mispresentations of his work I
might have presented. - pj ]
I've just started reading this - it seems well presented and I think
you have put much effort into it. Thank-you for posting it.
I have not yet taken the time to understand it properly, but a couple
of questions come to mind offhand. I hope these questions will not be
too silly.
1) What is the relation of this patch set to CKRM?
2) Would a structure similar to Dinakar's patches to connect
cpusets and dynamic sched domains (posted to linux-mm)
work here as well?
Let me describe what I see so far, and hope you will be patient with my
confusions. Then perhaps I can better explain my question (2) above.
My initial understanding is that subcpusets provide a way to partial
out the proportion of cpu and memory used by various tasks. A leaf
node cpuset can partition the tasks attached to it into subsets, called
subcpusets, where each subcpuset gets a proportion of cpu and memory
available to the original leaf node cpuset.
These original leaf node cpusets (the parents of the 'subcpusets') form
a non-overlapping and partial covering of the cpus and memory nodes in
a system. It is a _partial_ covering because not every leaf node
cpuset need be subdivided into 'subcpusets', nor does every cpu or
memory node need to be in such a cpuset.
I'm guessing you do not want such cpusets (the parents of subcpusets)
to overlap, because if they did, it would seem to confuse the meaning
of getting a fixed proportion of available cpu and memory resources. I
was a little surprised not to see any additional checks that
cpu_exclusive and mem_exclusive must be set true in these cpusets, to
insure non- overlapping cpusets.
Dinakar's patches used cpu_exclusive cpusets to form a complete
non-overlapping covering of the cpus in a system (the cpus not
in cpu_exclusive cpusets got their own separate covers). Then each
such cover defined a different dynamic sched domain (a separately
scheduled set of tasks).
Your cover elements (your subcpusets) seem to be a somewhat new kind of
cpuset, that can only occur as children of original leaf node cpusets.
Instead of that, I might prefer doing as Dinakar did, and use a single
boolean flag per existing cpuset, to mark a subset of the cpusets that
form the covering. Dinakar got lucky, and was able to use an existing
cpuset boolean flag - cpu_exclusive, which had not been very useful
until then. You will have to add a new flag.
On the other hand, Dinakar had more work to do than you might, because
he needed a complete covering (so had to round up cpus in non exclusive
cpusets to form more covering elements). From what I can tell, you
don't need a complete covering - it seems fine if some cpus are not
managed by this resource control function.
I hope my above remarks are not to far off the mark and do not misrepresent
your work too painfully. And I hope they make at least a little sense.
Sometimes I have a strange way of describing my thoughts.
Thank-you again for this good work. I look forward to your further
considerations. I will make the time soon to read this patch more
closely.
--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <[email protected]> 1.925.600.0401
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