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Donenfeld" To: David Hildenbrand Cc: Linus Torvalds , linux-kernel@vger.kernel.org, patches@lists.linux.dev, tglx@linutronix.de, linux-crypto@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, Greg Kroah-Hartman , Adhemerval Zanella Netto , Carlos O'Donell , Florian Weimer , Arnd Bergmann , Jann Horn , Christian Brauner , David Hildenbrand , linux-mm@kvack.org Subject: Re: [PATCH v21 1/4] mm: add VM_DROPPABLE for designating always lazily freeable mappings Message-ID: References: <6705c6c8-8b6a-4d03-ae0f-aa83442ec0ab@redhat.com> <7439da2e-4a60-4643-9804-17e99ce6e312@redhat.com> <75d6c45d-deea-464d-b0fd-b36e5d73b898@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 581541C0003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 67xwm5hgpi13nigaszgm86h9upbpyaun X-HE-Tag: 1720582472-444146 X-HE-Meta: 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 tiDKm0un J1ci9424/L+TpXFVSd/eNNIEIsqR4b9IGk1Ago7r/l76aV9FzT9YrLa+gzmBuwZ12V9cZK7upat54QNqTt6N656JsfwhJzaObMyJgfhZYgTmGcY9GbP/Y0NYuXdFsxFMECnWSJiuzLcrz/ukXwgJIwsO7eviBg/1V0dS+O0ohy0aK3nbsLAi3J9ttIordG9Rb4YuynRQSX6dVNyRIF1/ApEiI3oYy6GsOAxwmm1/Ii6JdFYdoxOaQ760lfnErKEHI1TlItkQGqf5KLYSzt+KB3OB4KiXhVdfYkw5HyVh/C/1LEYlg8uQrG43KKrEwMfJS7T5H1pf2R/IeUahGzIJE5cLWYBKbkP52qfOhpxsHgi4tP5UatR14bOYiwmmKGdYL4Bpjyfh7Skp9b+Ocs2VqvP+uhuvwf6ANHVK56patfcdi9I1WMn+E5AH34tSjZ99RJ2iWlw/5Y4tI+8Q= 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: List-Subscribe: List-Unsubscribe: On Wed, Jul 10, 2024 at 05:05:06AM +0200, David Hildenbrand wrote: > On 09.07.24 04:17, Jason A. Donenfeld wrote: > > Hi David, > > > > On Mon, Jul 08, 2024 at 10:21:09PM +0200, David Hildenbrand wrote: > >> BTW, I was just trying to understand how MADV_FREE + MAP_DROPPABLE would > >> behave without any swap space around. > >> > >> Did you experiment with that? > > > > You mean on a system without any swap configured? That's actually my > > primary test environment for this. It behaves as expected: when ram > > fills up and the scanner is trying to reclaim what it can, > > folio_test_swapbacked(folio) is false, and the memory gets freed. After, > > reads fault in a zero page. So it's working as expected. > > Okay, just to be clear: no swap/zram/zswap. The reclaim code regarding > not scanning anonymous memory without swap was a bit confusing. Right, no swap, as boring a system as can be. I've experimented with that behavior on my swap-less 64GB thinkpad, as well as on little special purpose VMs, where I hacked the VM_DROPPABLE test code into the wireguard test suite. Jason