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Message-ID: <20190408203541-mutt-send-email-mst@kernel.org> Date: Mon, 8 Apr 2019 22:44:25 -0400 From: "Michael S. Tsirkin" <mst@...hat.com> To: Alexander Duyck <alexander.duyck@...il.com> Cc: David Hildenbrand <david@...hat.com>, Nitesh Narayan Lal <nitesh@...hat.com>, kvm list <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>, Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com, pagupta@...hat.com, wei.w.wang@...el.com, Yang Zhang <yang.zhang.wz@...il.com>, Rik van Riel <riel@...riel.com>, dodgen@...gle.com, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, dhildenb@...hat.com, Andrea Arcangeli <aarcange@...hat.com> Subject: Re: Thoughts on simple scanner approach for free page hinting On Fri, Apr 05, 2019 at 05:09:45PM -0700, Alexander Duyck wrote: > In addition we will need some way to identify which pages have been > hinted on and which have not. The way I believe easiest to do this > would be to overload the PageType value so that we could essentially > have two values for "Buddy" pages. We would have our standard "Buddy" > pages, and "Buddy" pages that also have the "Offline" value set in the > PageType field. Tracking the Online vs Offline pages this way would > actually allow us to do this with almost no overhead as the mapcount > value is already being reset to clear the "Buddy" flag so adding a > "Offline" flag to this clearing should come at no additional cost. It bothers me a bit that this doesn't scale to multiple hint types if we ever need them. Would it be better to have two free lists: hinted and non-hinted one? -- MST
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