linux-kernel - Re: [PATCH 2/2] mm, thp: consolidate THP gfp handling into alloc_hugepage_direct

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Date:   Wed, 24 Oct 2018 16:17:54 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Michal Hocko <mhocko@...nel.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Mel Gorman <mgorman@...e.de>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Argangeli <andrea@...nel.org>,
        Zi Yan <zi.yan@...rutgers.edu>,
        Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm, thp: consolidate THP gfp handling into
 alloc_hugepage_direct_gfpmask

On Mon, 22 Oct 2018 15:27:54 +0200 Vlastimil Babka <vbabka@...e.cz> wrote:

> > : Moreover the oriinal code allowed to trigger
> > : 	WARN_ON_ONCE(policy->mode == MPOL_BIND && (gfp & __GFP_THISNODE));
> > : in policy_node if the requested node (e.g. cpu local one) was outside of
> > : the mbind nodemask. This is not possible now. We haven't heard about any
> > : such warning yet so it is unlikely that it happens but still a signal of
> > : a wrong code layering.
> 
> Ah, as I said in the other mail, I think it's inaccurate, the warning
> was not possible to hit.
> 
> There's also a slight difference wrt MPOL_BIND. The previous code would
> avoid using __GFP_THISNODE if the local node was outside of
> policy_nodemask(). After your patch __GFP_THISNODE is avoided for all
> MPOL_BIND policies. So there's a difference that if local node is
> actually allowed by the bind policy's nodemask, previously
> __GFP_THISNODE would be added, but now it won't be. I don't think it
> matters that much though, but maybe the changelog could say that
> (instead of the inaccurate note about warning). Note the other policy
> where nodemask is relevant is MPOL_INTERLEAVE, and that's unchanged by
> this patch.

So the above could go into the changelog, yes?

> When that's addressed, you can add

What is it that you'd like to see addressed?  Purely changelog updates?

> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks.