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[209.85.208.170]) by smtp.gmail.com with ESMTPSA id b17sm877341lfc.21.2018.11.27.14.50.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Nov 2018 14:50:22 -0800 (PST) Received: by mail-lj1-f170.google.com with SMTP id c19-v6so21624464lja.5 for ; Tue, 27 Nov 2018 14:50:22 -0800 (PST) X-Received: by 2002:a2e:9819:: with SMTP id a25-v6mr23475934ljj.6.1543359021483; Tue, 27 Nov 2018 14:50:21 -0800 (PST) MIME-Version: 1.0 References: <20181127062503.GH6163@shao2-debian> <20181127205737.GI16136@redhat.com> In-Reply-To: <20181127205737.GI16136@redhat.com> From: Linus Torvalds Date: Tue, 27 Nov 2018 14:50:05 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [LKP] [mm] ac5b2c1891: vm-scalability.throughput -61.3% regression To: Andrea Arcangeli Cc: rong.a.chen@intel.com, Michal Hocko , s.priebe@profihost.ag, alex.williamson@redhat.com, mgorman@techsingularity.net, zi.yan@cs.rutgers.edu, Vlastimil Babka , rientjes@google.com, kirill@shutemov.name, Andrew Morton , Linux List Kernel Mailing , lkp@01.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 27, 2018 at 12:57 PM Andrea Arcangeli wrote: > > This difference can only happen with defrag=always, and that's not the > current upstream default. Ok, thanks. That makes it a bit less critical. > That MADV_HUGEPAGE causes flights with NUMA balancing is not great > indeed, qemu needs NUMA locality too, but then the badness caused by > __GFP_THISNODE was a larger regression in the worst case for qemu. [...] > So the short term alternative again would be the alternate patch that > does __GFP_THISNODE|GFP_ONLY_COMPACT appended below. Sounds like we should probably do this. Particularly since Vlastimil pointed out that we'd otherwise have issues with the back-port for 4.4 where that "defrag=always" was the default. The patch doesn't look horrible, and it directly addresses this particular issue. Is there some reason we wouldn't want to do it? Linus