linux-kernel - Re: [patch 1/2 for-4.20] mm, thp: restore node-local hugepage allocations

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Message-ID: <20181205201528.GW1286@dhcp22.suse.cz>
Date:   Wed, 5 Dec 2018 21:15:28 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>, ying.huang@...el.com,
        s.priebe@...fihost.ag, mgorman@...hsingularity.net,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        alex.williamson@...hat.com, lkp@...org, kirill@...temov.name,
        Andrew Morton <akpm@...ux-foundation.org>,
        zi.yan@...rutgers.edu, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [patch 1/2 for-4.20] mm, thp: restore node-local hugepage
 allocations

On Wed 05-12-18 11:24:53, David Rientjes wrote:
> On Wed, 5 Dec 2018, Michal Hocko wrote:
> 
> > > > At minimum do not remove the cleanup part which consolidates the gfp
> > > > hadnling to a single place. There is no real reason to have the
> > > > __GFP_THISNODE ugliness outside of alloc_hugepage_direct_gfpmask.
> > > > 
> > > 
> > > The __GFP_THISNODE usage is still confined to 
> > > alloc_hugepage_direct_gfpmask() for the thp fault path, we no longer set 
> > > it in alloc_pages_vma() as done before the cleanup.
> > 
> > Why should be new_page any different?
> > 
> 
> To match alloc_new_node_page() which does it correctly and does not change 
> the behavior of mbind() that the cleanup did, which used 
> alloc_hugepage_vma() to get the __GFP_THISNODE behavior.  If there is a 
> reason mbind() is somehow different wrt allocating hugepages locally, I 
> think that should be a separate patch, but the goal of this patch is to 
> revert all the behavioral change that caused hugepages to be allocated 
> remotely.

If the __GFP_THISNODE should be really used then it should be applied to
all other types of pages. Not only THP. And as such done in a separate
patch. Not a part of the revert. The cleanup was meant to unify THP
allocations and that is why I object to reverting it as a part of this
work.

-- 
Michal Hocko
SUSE Labs