linux-kernel - Re: [RFC PATCH 2/4] hugetlb: add support for preferred node to alloc_huge_page

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Message-ID: <20170615081239.GC1486@dhcp22.suse.cz>
Date:   Thu, 15 Jun 2017 10:12:40 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/4] hugetlb: add support for preferred node to
 alloc_huge_page_nodemask

On Wed 14-06-17 17:12:31, Mike Kravetz wrote:
> On 06/14/2017 03:12 PM, Mike Kravetz wrote:
> > On 06/13/2017 02:00 AM, Michal Hocko wrote:
> >> From: Michal Hocko <mhocko@...e.com>
> >>
> >> alloc_huge_page_nodemask tries to allocate from any numa node in the
> >> allowed node mask starting from lower numa nodes. This might lead to
> >> filling up those low NUMA nodes while others are not used. We can reduce
> >> this risk by introducing a concept of the preferred node similar to what
> >> we have in the regular page allocator. We will start allocating from the
> >> preferred nid and then iterate over all allowed nodes in the zonelist
> >> order until we try them all.
> >>
> >> This is mimicking the page allocator logic except it operates on
> >> per-node mempools. dequeue_huge_page_vma already does this so distill
> >> the zonelist logic into a more generic dequeue_huge_page_nodemask
> >> and use it in alloc_huge_page_nodemask.
> >>
> >> Signed-off-by: Michal Hocko <mhocko@...e.com>
> >> ---
> > 
> > 
> > I built attempts/hugetlb-zonelists, threw it on a test machine, ran the
> > libhugetlbfs test suite and saw failures.  The failures started with this
> > patch: commit 7e8b09f14495 in your tree.  I have not yet started to look
> > into the failures.  It is even possible that the tests are making bad
> > assumptions, but there certainly appears to be changes in behavior visible
> > to the application(s).
> 
> nm.  The failures were the result of dequeue_huge_page_nodemask() always
> returning NULL.  Vlastimil already noticed this issue and provided a
> solution.

I have pushed my current version to the same branch.
-- 
Michal Hocko
SUSE Labs