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[173.76.246.42]) by smtp.gmail.com with ESMTPSA id v4sm17179402qtq.94.2019.04.09.06.37.56 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 09 Apr 2019 06:37:57 -0700 (PDT) Date: Tue, 9 Apr 2019 09:37:54 -0400 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: Alexander Duyck , 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: Thoughts on simple scanner approach for free page hinting Message-ID: <20190409093642-mutt-send-email-mst@kernel.org> References: <20190409092625-mutt-send-email-mst@kernel.org> <43aa1bd2-4aac-5ac4-3bd4-fe1e4a342c79@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43aa1bd2-4aac-5ac4-3bd4-fe1e4a342c79@redhat.com> 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 09, 2019 at 03:36:08PM +0200, David Hildenbrand wrote: > On 09.04.19 15:31, Michael S. Tsirkin wrote: > > On Tue, Apr 09, 2019 at 11:20:36AM +0200, David Hildenbrand wrote: > >> BTW I like the idea of allocating pages that have already been hinted as > >> last "choice", allocating pages that have not been hinted yet first. > > > > OK I guess but note this is just a small window during which > > not all pages have been hinted. > > Yes, good point. It might sound desirable but might be completely > irrelevant in practice. > > > > > So if we actually think this has value then we need > > to design something that will desist and not drop pages > > in steady state too. > > By dropping, you mean dropping hints of e.g. MAX_ORDER - 1 or e.g. not > reporting MAX_ORDER - 3? I mean the issue is host unmaps the pages from guest right? That is what makes hinted pages slower than non-hinted ones. If we do not want that to happen for some pages, then either host can defer acting on the hint, or we can defer hinting. > -- > > Thanks, > > David / dhildenb