cpuset and affinity implementation
jroberson at chesapeake.net
Tue Feb 26 01:10:26 UTC 2008
On Mon, 25 Feb 2008, Brooks Davis wrote:
> On Sun, Feb 24, 2008 at 05:38:37PM -1000, Jeff Roberson wrote:
>> I have implemented a new api similar to processors sets on solaris. This
>> allows you to assign processes to sets of cpus and dynamically change those
>> sets. This is useful for provisioning purposes to add and remove cpu
>> resources for a particular process or group of processes. This new
>> facility also supports binding secific threads to specific cpus which some
>> applications may want to do. At some point in the future this will be
>> integrated with jail so you can restrict the cpus any jail is allowed to
>> This api should not be considered final and the 'cpuset' tool is quite
>> rough. This also only works with ULE and is unfortunately intertwined with
>> a big ULE patch I've been working on. The set management code is generic
>> but 4BSD doesn't contain the hooks to actually constrain threads.
> I took a look at the patch this morning. The API looks like it's
> capable of doing what I need, at least at a first pass. It looks like I
> should be able to implement the semantics currently employed by the Sun
> Grid Engine scheduler on Irix systems.
> The one thing I noticed that I found worrying was the recursion in
> cpuset_(test)update(). It wasn't immediately clear to me there there
> is anything to would prevent an arbitrarily deep hierarchy from being
> created and blowing the kernel stack. I'm I missing something?
Yes, presently it can never be more than 3 levels deep. Once we have
jails the max would be 6 levels, unless you can make jails within jails.
There is presently now way for the user to create a cpuset that is a
subset of another set. So the three cpu sets are:
1) Root set - immutable, all cpus, may be root of jail in which case root
outside of the jail can change the set.
2) cpuset - the set this process is a member of.
3) mask - the anonymous set that is applied to an individual thread.
Did you look at the userland tool at all? I think this needs the most
improvement. I basically just made something that would allow me to pass
every possible parameter to the api. Not exactly engineered for
> -- Brooks
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