Linux compatible setaffinity.

[Jeff Roberson]

On Wed, 20 Feb 2008, Daniel Eischen wrote:

> On Tue, 19 Feb 2008, Jeff Roberson wrote:
>
>> On Sat, 12 Jan 2008, Jeff Roberson wrote:
>> 
>>> On Sat, 12 Jan 2008, Daniel Eischen wrote:
>>> 
>>>> On Sat, 12 Jan 2008, Jeff Roberson wrote:
>>>> 
>>>>> Now, there is one problem with the linux api that I want to discuss 
>>>>> before I commit it.  The current patch always works on curthread. 
>>>>> However, the api allows for setting the binding of a pid.  I believe, 
>>>>> although I'm not certain, that pids and tids in linux are in the same 
>>>>> number space.  It's not clear to me whether you can set an affinity for 
>>>>> an entire process and have it effect an individual thread or whether you 
>>>>> set it on a thread by thread basis.  When supplying a non-curproc pid do 
>>>>> you bind all threads in the target process?
>>>>> 
>>>>> Are our tids and pids in the same number space?  And are they available 
>>>>> to application programmers?  I haven't followed that very carefully.
>>>> 
>>>> I believe marcel made tids and pids disjoint so that any pid is
>>>> never equal to any tid.  But regardless, I don't think we want
>>>> to rely on that.  I would prefer the Solaris approach of specifying
>>>> what we want (pid, tid, jail id, etc) as an argument in the API
>>>> so there is no confusion.
>>> 
>>> Yes, I would prefer that as well I believe.  So I'll add an extra 
>>> parameter and in the linux code we'll use whatever their default is.  Of 
>>> course the initial implementation will still only support curthread but I 
>>> plan on finishing the rest before 8.0 is done.
>> 
>> So what does everyone think of something like this:
>> 
>> int cpuaffinity(int cmd, long which, int masksize, unsigned *mask);
>> 
>> #define AFFINITY_GET	0x1
>> #define	AFFINITY_SET	0x2
>> #define	AFFINITY_PID	0x4
>> #define	AFFINITY_TID	0x8
>> 
>> I'm not married to any of these names.  If you know of something that would 
>> be more regular please comment.
>
> I take it 'cmd' is either AFFINITY_GET or AFFINITY_SET, and which
> is AFFINITY_PID or AFFINITY_TID.  Is there a reason why, for 2 different
> arguments to cpuaffinity(), the flags are disjoint?  It almost seems
> like you wanted:
>
> 	int cpuaffinity(int flags, int masksize, unsigned *mask)
>
> I prefer the API you specified, keeping 'cmd' and 'which' as
> separate arguments.
>

Yes, I'll either do that or have seperate get/set syscalls.

> Is masksize in bytes or in units of unsigned?  Do we need helper
> functions/macros for the mask?  Like sigemptyset, sigaddset, etc?

I have macros copied from FD_SET, as CPU_SET, CPU_ISSET, etc.

This will go in sys/sched.h.

>
> -- 
> DE
>