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SubjectRe: [ckrm-tech] [RFC] Resource Management - Infrastructure choices
Paul M wrote:
> The cpusets code which this was based on simply locked the task list,
> and traversed it to find threads in the cpuset of interest; you could
> do the same thing in any other resource controller.

I get away with this in the cpuset code because:
1) I have the cpuset pointer directly in 'task_struct', so don't
have to chase down anything, for each task, while scanning the
task list. I just have to ask, for each task, if its cpuset
pointer points to the cpuset of interest.
2) I don't care if I get an inconsistent answer, so I don't have
to lock each task, nor do I even lockout the rest of the cpuset
code. All I know, at the end of the scan, is that each task that
I claim is attached to the cpuset in question was attached to it at
some point during my scan, not necessarilly all at the same time.
3) It's not a flaming disaster if the kmalloc() of enough memory
to hold all the pids I collect in a single array fails. That
just means that some hapless users open for read of a cpuset
'tasks' file failed, -ENOMEM. Oh well ...

If someone is actually trying to manage system resources accurately,
they probably can't get away being as fast and loose as this.

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <pj@sgi.com> 1.925.600.0401
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