RE: [Lse-tech] Re: CPUSET Proposal

["Yu, Fenghua" <fenghua.yu@intel.com>]

>> You could also do a big chunk of this by allowing normal 
>> privledge users
>> to sched_setaffinity() a *subset* of their current allowed 
>> CPU set, but
>> not expand it.  sched_setaffinity() isn't *that* old of an 
>> interface, so
>> I'm not sure why you can't just change the application at 
>> this point.  

>Because you need virtual cpu numbers.  Suppose I have a 16-way
>system, and *two* applications that know nothing about each other,
>but each happens to want 5 cpus to run.

>With cpusets each application can ask the kernel for 5 cpus
>(or a wrapper that invokes the application can do so), and then
>the application can happily divide its work between virtual cpus
>0, 1, 2, 3, 4 (using sched_setaffinity()).  The kernel can be smart
>and provide different physical cpus for each of the cpusets.

In this case, the applications can get all of current affinity info by
calling sched_getaffinity(). Thus, the applications can schedule the
processes to different cpus without bothering kernel.