Re: [patch 2/2] cpusets: add interleave_over_allowed option

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 

On Fri, 26 Oct 2007, Paul Jackson wrote:

> > Yes. We should default to Choice B. Add an option MPOL_MF_RELATIVE to 
> > enable that functionality? A new version of numactl can then enable
> > that by default for newer applications.
> 
> I'm confused.  If B is the default, then we don't need a flag to
> enable it, rather we need a flag to go back to the old choice A.
> 

I think there's a mixup in the flag name there, but I actually would 
recommend against any flag to effect Choice A.  It's simply going to be 
too complex to describe and is going to be a headache to code and support.  

The MPOL_PREFERRED behavior when constrained by cpusets was previously, to 
my knowledge, undocumented; you're in the position to make the behavior do 
what you want it to do and then release documentation so we'll finally 
have a complete and unambiguous API for it.  Right now it should be 
considered undefined and thus you are free to implement it as you choose.  
Then all callers of set_mempolicy(MPOL_PREFERRED) will standardize on that 
and not have to worry about the machine's 
mpol_preferred_relative_to_cpuset setting.

Then, any task that is attached to a cpuset and expecting the fourth node 
in their set_mempolicy(MPOL_PREFERRED) call to mean system node 3 if 
it's in the cpuset's mems_allowed will be broken.  If you want that, 
you'll need your task to be attached to a cpuset with at least mems 0-3; 
programmers will pick that up quickly enough if it's clearly documented.
I think Choice B is correct and makes more sense in terms of the semantics 
and at least allows mempolicies and cpusets to play nicely together 
without a bidirectional dependency on one another.

		David
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux