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[209.85.220.41]) by mx.google.com with SMTPS id f9sor14082103qvr.51.2019.04.02.08.25.15 for (Google Transport Security); Tue, 02 Apr 2019 08:25:15 -0700 (PDT) Received-SPF: pass (google.com: domain of mst@redhat.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; Authentication-Results: mx.google.com; spf=pass (google.com: domain of mst@redhat.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=mst@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Google-Smtp-Source: APXvYqwU2x/6XRs2Azjaky+XbQ7todIFJAnFK2yBCuWt+46dnJIjuwQoRZKqLUKdiA2YPkTMxWJ6bg== X-Received: by 2002:a0c:d07b:: with SMTP id d56mr58838282qvh.89.1554218715324; Tue, 02 Apr 2019 08:25:15 -0700 (PDT) Received: from redhat.com ([66.187.232.66]) by smtp.gmail.com with ESMTPSA id a8sm7988404qtc.19.2019.04.02.08.25.12 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 02 Apr 2019 08:25:13 -0700 (PDT) Date: Tue, 2 Apr 2019 11:25:10 -0400 From: "Michael S. Tsirkin" To: Alexander Duyck Cc: David Hildenbrand , Nitesh Narayan Lal , kvm list , LKML , linux-mm , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli Subject: Re: On guest free page hinting and OOM Message-ID: <20190402112115-mutt-send-email-mst@kernel.org> References: <20190329125034-mutt-send-email-mst@kernel.org> <20190401073007-mutt-send-email-mst@kernel.org> <29e11829-c9ac-a21b-b2f1-ed833e4ca449@redhat.com> <20190401104608-mutt-send-email-mst@kernel.org> <6a612adf-e9c3-6aff-3285-2e2d02c8b80d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 02, 2019 at 08:04:00AM -0700, Alexander Duyck wrote: > Basically what we would be doing is providing a means for > incrementally transitioning the buddy memory into the idle/offline > state to reduce guest memory overhead. It would require one function > that would walk the free page lists and pluck out pages that don't > have the "Offline" page type set, I think we will need an interface that gets an offline page and returns the next online free page. If we restart the list walk each time we can't guarantee progress. > a one-line change to the logic for > allocating a page as we would need to clear that extra bit of state, > and optionally some bits for how to handle the merge of two "Offline" > pages in the buddy allocator (required for lower order support). It > solves most of the guest side issues with the free page hinting in > that trying to do it via the arch_free_page path is problematic at > best since it was designed for a synchronous setup, not an > asynchronous one. -- MST