linux-kernel - Re: [PATCH v3 0/1] man/set_mempolicy.2,mbind.2: add MPOL

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Message-ID: <alpine.DEB.2.20.1610120906150.14274@east.gentwo.org>
Date:   Wed, 12 Oct 2016 09:08:31 -0500 (CDT)
From:   Christoph Lameter <cl@...ux.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
cc:     Piotr Kwapulinski <kwapulinski.piotr@...il.com>,
        kirill.shutemov@...ux.intel.com, vbabka@...e.cz,
        rientjes@...gle.com, mhocko@...nel.org,
        mgorman@...hsingularity.net, liangchen.linux@...il.com,
        nzimmer@....com, a.p.zijlstra@...llo.nl, riel@...hat.com,
        lee.schermerhorn@...com, jmarchan@...hat.com, joe@...ches.com,
        corbet@....net, iamyooon@...il.com, n-horiguchi@...jp.nec.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-man@...r.kernel.org, akpm@...ux-foundation.org,
        linux-doc@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v3 0/1] man/set_mempolicy.2,mbind.2: add MPOL_LOCAL NUMA
 memory policy documentation

On Wed, 12 Oct 2016, Michael Kerrisk (man-pages) wrote:

> > +arguments must specify the empty set. If the "local node" is low
> > +on free memory the kernel will try to allocate memory from other
> > +nodes. The kernel will allocate memory from the "local node"
> > +whenever memory for this node is available. If the "local node"
> > +is not allowed by the process's current cpuset context the kernel
> > +will try to allocate memory from other nodes. The kernel will
> > +allocate memory from the "local node" whenever it becomes allowed
> > +by the process's current cpuset context. In contrast
> > +.B MPOL_DEFAULT
> > +reverts to the policy of the process which may have been set with
> > +.BR set_mempolicy (2).
> > +It may not be the "local allocation".
>
> What is the sense of "may not be" here? (And repeated below).
> Is the meaning "this could be something other than"?
> Presumably the answer is yes, in which case I'll clarify
> the wording there. Let me know.

Someone may have set for example a round robin policy with numactl
--interleave before starting the process? Then allocations will go through
all nodes.