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Message-ID: <20220207173953.GD12302@lespinasse.org> Date: Mon, 7 Feb 2022 09:39:53 -0800 From: Michel Lespinasse <michel@...pinasse.org> To: Matthew Wilcox <willy@...radead.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, Michel Lespinasse <michel@...pinasse.org>, Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org, kernel-team@...com, Laurent Dufour <ldufour@...ux.ibm.com>, Jerome Glisse <jglisse@...gle.com>, Peter Zijlstra <peterz@...radead.org>, Michal Hocko <mhocko@...e.com>, Vlastimil Babka <vbabka@...e.cz>, Davidlohr Bueso <dave@...olabs.net>, Liam Howlett <liam.howlett@...cle.com>, Rik van Riel <riel@...riel.com>, Paul McKenney <paulmck@...nel.org>, Song Liu <songliubraving@...com>, Suren Baghdasaryan <surenb@...gle.com>, Minchan Kim <minchan@...gle.com>, Joel Fernandes <joelaf@...gle.com>, David Rientjes <rientjes@...gle.com>, Axel Rasmussen <axelrasmussen@...gle.com>, Andy Lutomirski <luto@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de> Subject: Re: [PATCH v2 00/35] Speculative page faults On Tue, Feb 01, 2022 at 02:20:39AM +0000, Matthew Wilcox wrote: > On Mon, Jan 31, 2022 at 05:14:34PM -0800, Andrew Morton wrote: > > On Fri, 28 Jan 2022 05:09:31 -0800 Michel Lespinasse <michel@...pinasse.org> wrote: > > > The next step is to walk down the existing page table tree to find the > > > current pte entry. This is done with interrupts disabled to avoid > > > races with munmap(). > > > > Sebastian, could you please comment on this from the CONFIG_PREEMPT_RT > > point of view? > > I am not a fan of this approach. For other reasons, I think we want to > switch to RCU-freed page tables, and then we can walk the page tables > with the RCU lock held. Some architectures already RCU-free the page > tables, so I think it's just a matter of converting the rest. Note - I have no problem with switching to RCU-freed page tables everywhere when and if we end up needing to. I just don't see that this need comes from the SPF patchset, so I don't think this should be introduced as an artificial dependency. -- Michel "walken" Lespinasse
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