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SubjectRe: [RFC] cpuset relative memory policies - second choice
On Wed, 31 Oct 2007, Paul Jackson wrote:

> > You are managing it in the task struct. No need to. libnuma can handle it.
>
> No - as noted, not all mempolicy system calls go via libnuma.

Well then show me.

> > No current version of libcpuset is available.
>
> Wrong. It has not received wide publication yet, but it has been
> provided to various others under LGPL license.

The last version that I remember was for 2.4.x.

> A search of some old SGI release software sitting on an internal
> server just now suggests that products with names including histx,
> gru, libmpi and pcp might be directly invoking these system calls
> ... I didn't actually examine the source to determine whether
> they really use these direct calls -- just got a grep hit.

A good argument to leave the API unchanged and not create magic task
flags.

> > > With the mode bit as in my patch, there are fewer places in the user
> > > code that have to be gotten just right. With your way, each and
> > > every mbind and *_mempolicy call has to be hacked with the new flag
> > > if one is going to use the new nodemask bit numbering. Some of these
> >
> > Yes and that makes sure it is thought through and done right.
>
> Maybe for you. Not for the rest of us error prone mere mortals.

> Forcing coders to specify the same detail in multiple places, when
> there is no way to validate their consistency, doesn't force them
> to think or do it right. It increases the error rate due to

There are always wrappers for system calls. The flags will be set in
these.
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