Paul Jackson wrote:
Diego wrote:
I bet I'm not the only one here
who can't understand it either.....
You're not alone.
See an email thread entitled:
Classes: 1) what are they, 2) what is their name?
http://sourceforge.net/mailarchive/forum.php?thread_id=5328162&forum_id=35191
on the [email protected] email list between Aug 14 and Aug
27, 2004, where I did my best to encourage the CKRM project to address
this problem. To no avail.
That is not really a fair categorization of the thread. Hubertus and I
did try to explain what CKRM classes are. As the last parts of the
thread show, it was the choice of names that you disagreed with.
Apparently, to some of the smartest amongst us, who got to hear
live presentations describing CKRM, it makes sense and is worthy
of serious consideration.
Except for the Kernel Summit talk (slides of which were very brief),
you have access to the very same presentations on the ckrm website.
For myself, of more ordinary intelligence and working just from the
documentation and an occassional glance at the code, it has been a
difficult proposal to understand, with a rather large patch requiring
some non-trivial kernel hooks.
Have you read Section 2 of the
http://ckrm.sourceforge.net/downloads/ckrm-ols04-paper.pdf
There the terms class, classtype, resource controllers and
classification engine have all been explained. If you continue to have
trouble understanding what these mean, we'd be happy to go over it once
more. Perhaps we should try a twiki type site or come up with a specific
set of doubts that need to be addressed.
A question for the CKRM developers:
What middleware packages, outside the kernel, exist or are
in the works that will rely on CKRM?
CKRM (like another project near and dear to me, cpusets)
strikes me as a "middleware foundation" facility, intended
to provide the essential kernel support required for some
serious enterprise software. So perhaps in addition to
asking what end-users (of a combined kernel-middleware
platform) exist, we should also be asking who will be
directly using CKRM - directly layering middleware on top
of it.
The details don't matter much and may have to remain
obscured in the competitive fog. But the presence of
multiple groups lobbying for the same kernel infrastructure,
as an apparent basis for competing middleware products,
would I think weigh in CKRM's favor.
Undoubtedly so. However, workload management middleware developers don't
seem to have a history of actively participating in LKML for useful
features so its left to the likes of us to determine what *would* be
useful and then go build it if it makes sense and is acceptable to the
community.
My impression, which may not align with how the CKRM developers view
things, is that CKRM is descendent from what have been called fair-share
schedulers. The following comes from the above email thread.
Doing fair-share scheduling is indeed the ultimate goal of CKRM. But
using that characterization *alone* will not, in my opinion, be
sufficient to explain what are classes, classtypes etc.
No doubt the CKRM experts are already familiar with these, but for the
possible benefit of other readers:
UNICOS Resource Administration - Chapter 4. Fair-share Scheduler
http://oscinfo.osc.edu:8080/dynaweb/all/004-2302-001/@Generic__BookTextView/22883
SHARE II -- A User Administration and Resource Control System for UNIX
http://www.c-side.com/c/papers/lisa-91.html
Solaris Resource Manager White Paper
http://wwws.sun.com/software/resourcemgr/wp-mixed/
ON THE PERFORMANCE IMPACT OF FAIR SHARE SCHEDULING
http://www.cs.umb.edu/~eb/goalmode/cmg2000final.htm
A Fair Share Scheduler, J. Kay and P. Lauder
Communications of the ACM, January 1988, Volume 31, Number 1, pp 44-55.
Thanks for the links. Yes, some of these are useful in understanding the
utility of fair-share scheduling and may even help in creating better
"controllers" in CKRM-speak.
-- Shailabh
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