Re: New Metrics to measure Load average
From: sena seneviratne
Date: Fri Jun 16 2006 - 02:47:45 EST
Hi Peter,
(1) Yes it would be a good idea to separate them for each CPU. The we have
that as an information too.
Out project is as follows:
Our project which is conducted as part of CEL(and CSIRO) requires to
separate the load along individual user lines.
This project is a GRID computing project.
We have developed a prediction model called "Free Load Profile Model for
Load Profile Prediction" for the purpose of scheduling in the Grid.
Irrespective of number of CPUs in the system we need to know the total
load which has been exerted on all CPUs (on the system) by individual users
and system/root.
As required by the prediction model then we need to know the break down
of that load along the user lines.
It is up to the prediction model to handle the issues with number CPUs as
it has such a capability.
(2) I am working at Electrical Engineering. My number until next Tuesday
would be 93517227.
IF you are living close to the Sydney Uni we will be able to discuss things
later.
I had a discussion with Rusty Russel and he had few suggestions for me too.
Thanks
Sena Seneviratne
Computer Engineering Lab
School of Electrical and Information Engineering
Sydney University
Australia
At 03:42 PM 6/16/2006 +1000, you wrote:
sena seneviratne wrote:
Hi Shailabh,Vadim,
Zoltan, Peter Williams,
David Osojnik, Nishanth Aravamudan,
Balbir Singh, Andrew Morton
(1) Please give us your valuable comments on this important change to
introduce a new Metric to measure Load average.
Currently /proc/loadavg reports only the resultant value.
We have done the scheduling in a Grid project. As a part of that we had
to do some changes to the Linux kernel as well.
The problem with the load metric of current Linux/Unix is that it
measures CPU load and Disk load without indicating the true nature of the
load, thereby creating some confusion among the readers. For example, if
a CPU bound task switches on to read a large chunk of disk data, then the
load average value would still continue to indicate this activity as a
load, yet the true CPU load during this period would have been zero. This
situation triggered us to make necessary additions to the kernel so that
CPU load and Disk load could be reported separately. Further the
specialisation of load helped our model to perform predictions when there
is interference between CPU and Disk IO loads.
In the user mode, a new proc file called /proc/loadavgus would collect
the new data according to a new format which would look like the following,
CPU Disk
500 0.7 0
501 0.9 1
502 0.9 0
503 1.03 1
504 0.93 0
505 1.0 0
What do you think about this change?
I think that it is useful to have the separate components (cpu and disk
I/O) of the load average available but, while I have no objection to the
data being made available on a per user basis, I think that it should
primarily be provided on a per CPU and total system basis. This is
because most people are only interested in the loads for the system as a
whole while per CPU data is a good indication of how well load balancing
is working.
This latter observation leads me to suggest that "weighted" CPU load per
CPU would also be useful. So output like:
CPU0 0.3 0.45 0.9
CPU1 0.4 0.5 0.8
TOTAL 0.7 0.95 1.7
would be nice to have where the columns were raw CPU load, weighted CPU
load and disk I/O load respectively.
In summary, I like the idea but think that you should do it properly and
provide the data that will interest most users and then add the per user
data that meets your specific needs as an optional extra.
Peter
PS I live very close to Sydney University if you want to discuss these
ideas in person.
--
Peter Williams pwil3058@xxxxxxxxxxxxxx
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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