Re: [RFC] eal: add cgroup-aware resource self discovery

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

Hi Neil,

On 1/25/2016 9:46 PM, Neil Horman wrote:
> On Mon, Jan 25, 2016 at 02:49:53AM +0800, Jianfeng Tan wrote:
...
>> -- 
>> 2.1.4
>>
>>
>
> This doesn't make a whole lot of sense, for several reasons:
>
> 1) Applications, as a general rule shouldn't be interrogating the cgroups
> interface at all.

The main reason to do this in DPDK is that DPDK obtains resource 
information from sysfs and proc, which are not well containerized so 
far. And DPDK pre-allocates resource instead of on-demand gradual 
allocating.

>
> 2) Cgroups aren't the only way in which a cpuset or memoryset can be restricted
> (the isolcpus command line argument, or a taskset on a parent process for
> instance, but there are several others).

Yes, I agree. To enable that, I'd like design the new API for resource 
self discovery in a flexible way. A parameter "type" is used to specify 
the solution to discovery way. In addition, I'm considering to add a 
callback function pointer so that users can write their own resource 
discovery functions.

>
> Instead of trying to figure out what cpuset is valid for your process by
> interrogating the cgroups heirarchy, instead you should follow the proscribed
> method of calling sched_getaffinity after calling sched_setaffinity.  That will
> give you the canonical cpuset that you are executing on, taking all cpuset
> filters into account (including cgroups and any other restrictions).  Its far
> simpler as well, as it doesn't require a ton of file/string processing.

Yes, this way is much better for cpuset discovery. But is there such a 
syscall for hugepages?

Thanks,
Jianfeng

>
> Neil
>