linux-kernel - Re: [RFC V2 02/12] mm: Isolate HugeTLB allocations away from CDM nodes

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Date:   Wed, 1 Feb 2017 11:01:35 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     mhocko@...e.com, vbabka@...e.cz, mgorman@...e.de,
        minchan@...nel.org, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, srikar@...ux.vnet.ibm.com,
        haren@...ux.vnet.ibm.com, jglisse@...hat.com,
        dan.j.williams@...el.com
Subject: Re: [RFC V2 02/12] mm: Isolate HugeTLB allocations away from CDM
 nodes

On 02/01/2017 05:59 AM, Anshuman Khandual wrote:
> So shall we write all these details in the comment section for each
> patch after the SOB statement to be more visible ? Or some where
> in-code documentation as FIXME or XXX or something. These are little
> large paragraphs, hence was wondering.

I would make an effort to convey a maximum amount of content in a
minimal amount of words. :)

But, yeah, it is pretty obvious that you've got too much in the cover
letter and not enough in the patches descriptions.

...
> * Page faults (which will probably use __GFP_THISNODE) cannot come from the
>   CDM nodes as they dont have any CPUs.

Page faults happen on CPUs but they happen on VMAs that could be bound
to a CDM node.  We allocate based on the VMA policy first, the fall back
to the default policy which is based on the CPU doing the fault if the
VMA doesn't have a specific policy.