linux-kernel - Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression

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Date:   Mon, 3 Dec 2018 12:39:34 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        ying.huang@...el.com, Andrea Arcangeli <aarcange@...hat.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: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3%
 regression

On Mon, 3 Dec 2018, Michal Hocko wrote:

> I have merely said that a better THP locality needs more work and during
> the review discussion I have even volunteered to work on that. There
> are other reclaim related fixes under work right now. All I am saying
> is that MADV_TRANSHUGE having numa locality implications cannot satisfy
> all the usecases and it is particurarly KVM that suffers from it.

I think extending functionality so thp can be allocated remotely if truly 
desired is worthwhile just so long as it does not cause regressions for 
other users.  I think that is separate from the swap storm regression that 
Andrea is reporting, however, since that would also exist even if we 
allowed remote thp allocations when the host is fully fragmented rather 
than only locally fragmented.