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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id u18sm36087109qkj.98.2019.08.06.06.40.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 06 Aug 2019 06:40:32 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1huzhW-0004zI-Ru; Tue, 06 Aug 2019 10:40:30 -0300 Date: Tue, 6 Aug 2019 10:40:30 -0300 From: Jason Gunthorpe To: "Michael S. Tsirkin" Cc: Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH V2 7/9] vhost: do not use RCU to synchronize MMU notifier with worker Message-ID: <20190806134030.GD11627@ziepe.ca> References: <20190801141512.GB23899@ziepe.ca> <42ead87b-1749-4c73-cbe4-29dbeb945041@redhat.com> <20190802124613.GA11245@ziepe.ca> <20190802100414-mutt-send-email-mst@kernel.org> <20190802172418.GB11245@ziepe.ca> <20190803172944-mutt-send-email-mst@kernel.org> <20190804001400.GA25543@ziepe.ca> <20190804040034-mutt-send-email-mst@kernel.org> <20190806115317.GA11627@ziepe.ca> <20190806093633-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190806093633-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 06, 2019 at 09:36:58AM -0400, Michael S. Tsirkin wrote: > On Tue, Aug 06, 2019 at 08:53:17AM -0300, Jason Gunthorpe wrote: > > On Sun, Aug 04, 2019 at 04:07:17AM -0400, Michael S. Tsirkin wrote: > > > > > > Also, why can't this just permanently GUP the pages? In fact, where > > > > > > does it put_page them anyhow? Worrying that 7f466 adds a get_user page > > > > > > but does not add a put_page?? > > > > > > > > You didn't answer this.. Why not just use GUP? > > > > > > > > Jason > > > > > > Sorry I misunderstood the question. Permanent GUP breaks lots of > > > functionality we need such as THP and numa balancing. > > > > Really? It doesn't look like that many pages are involved.. > > > > Jason > > Yea. But they just might happen to be heavily accessed ones.... Maybe you can solve the numa balance problem some other way and use normal GUP.. Jason