[fpc-pascal] Re: GetAffinity\SetAffinity

[Mark Morgan Lloyd]

Brian wrote:
> After a bit of research , the issue of setting the cpu affinity has been
> solved , which may be of use to other folks.
> 
> A bit of info here concerning the data type cpu_set_t , which as far as I
> can determine (no help from the mess that is the c library source) is
> essentially an array of DWORD. For my purposes running on an x86 CPU ,
> allowance for 32 cores is sufficient , using cpu_set_1 as one unsigned long
> word.
> 
> http://www.cyberciti.biz/tips/setting-processor-affinity-certain-task-or-process.html
> 
> Here are some code fragments which may be of help.
> 
> 
> The function do_SysCall(0) basically doesn't work for setting the CPU core.
> 
> Although the Linux documentation claims sched_setaffinity() amd
> sched_getaffinity() work for threads  , it only works for processes. 
> 
> pthread_getaffinity_np() and pthread_setaffinity_np() work properly for
> threads.

Thanks for that, interesting. I'd have expected affinity to have been 
oriented towards processes rather than threads, since I think it largely 
originated when people started working on NUMA systems- possibly at SGI.

There's also interrupt affinity, which becomes significant when (the bus 
associated with) an I/O device is "nearer" some CPUs than others. I've 
had hardware of this type in the past, but in those days kernel support 
for these calls was patchy.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]