linux-kernel - Re: [patch for-5.3 0/4] revert immediate fallback to remote hugepages

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Date:   Tue, 5 Nov 2019 14:02:53 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [patch for-5.3 0/4] revert immediate fallback to remote hugepages

On Tue 29-10-19 16:25:17, David Rientjes wrote:
> On Tue, 29 Oct 2019, Andrew Morton wrote:
> 
> > On Tue, 29 Oct 2019 16:15:49 +0100 Michal Hocko <mhocko@...nel.org> wrote:
> > 
> > > > 
> > > > 1. local node only THP allocation with no reclaim, just compaction.
> > > > 2. for madvised VMA's or when synchronous compaction is enabled always - THP
> > > >    allocation from any node with effort determined by global defrag setting
> > > >    and VMA madvise
> > > > 3. fallback to base pages on any node
> > > > 
> > > > Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> > > 
> > > I've given this a try and here are the results of my previous testcase
> > > (memory full of page cache).
> > 
> > Thanks, I'll queue this for some more testing.  At some point we should
> > decide on a suitable set of Fixes: tags and a backporting strategy, if any?
> > 
> 
> I'd strongly suggest that Andrea test this patch out on his workload on 
> hosts where all nodes are low on memory because based on my understanding 
> of his reported issue this would result in swap storms reemerging but 
> worse this time because they wouldn't be constrained only locally.  (This 
> patch causes us to no longer circumvent excessive reclaim when using 
> MADV_HUGEPAGE.)

Could you be more specific on why this would be the case? My testing is
doesn't show any such signs and I am effectivelly testing memory low
situation. The amount of reclaimed memory matches the amount of
requested memory.

-- 
Michal Hocko
SUSE Labs