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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: <20240707002658.1917440-1-Jason@zx2c4.com> <20240707002658.1917440-2-Jason@zx2c4.com> <1583c837-a4d5-4a8a-9c1d-2c64548cd199@redhat.com> <6705c6c8-8b6a-4d03-ae0f-aa83442ec0ab@redhat.com> <7439da2e-4a60-4643-9804-17e99ce6e312@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7439da2e-4a60-4643-9804-17e99ce6e312@redhat.com> X-Stat-Signature: utnfhgqairfmhstso4ywiat3e9ozp4n9 X-Rspamd-Queue-Id: 2BC5F140003 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1720446957-670710 X-HE-Meta: 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 3+6m0uH2 maMSRtTVJe/aaIlmwL24X8AVJiZEW7OQ9rSJWWsMzO9TYxCo1rivYDr7DgF8gXkDSxwGYQFeLKAbGXNZpPXguhtyvoOHeDZhNS+PjkA6svK+OQgQf+KH3qVbFMvHz2EPPvxg9cSQLK3sYJs9K2CSLsTLRo7Chl1B5/6ZqYuk/dTZrrQd8jY8fIMC5NGLbOHIm3HlQnZiWakxM8Mcq3lejcK3rB5VaQ/x4Hb8APQlo0SYUAXOlI6OrjYDJ8099h5zvJqySl4iECgr5SAdZUqFqaJ1okRgE/geScmIb1+nE6FqjSyqsWDlgasviY7Vyaa1L3hvJ9pAJ90s0kdYoJWvlnoT0p19mj9qlfrP0NTgscvhhfurna+4ZqbdHPyHNKnupRVAwI0d0I09bWMnHBG8WxWiEqB3HcVLeP35p87qsMylYvxqQNcaBzFa0CptzKpT3ocRHIeUXNcJBp1A= 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: Hi David, On Mon, Jul 08, 2024 at 10:11:24AM +0200, David Hildenbrand wrote: > The semantics are much more intuitive. No need for separate mmap flags. Agreed. > Likely we'll have to adjust mlock() as well. Also, I think we should > just bail out with hugetlb as well. Ack. > Further, maybe we want to disallow madvise() clearing these flags here, > just to be consistent. Good thinking. > As a side note, I'll raise that I am not a particular fan of the > "droppable" terminology, at least with the "read 0s" approach. > > From a user perspective, the memory might suddenly lose its state and > read as 0s just like volatile memory when it loses power. "dropping > pages" sounds more like an implementation detail. > > Something like MAP_VOLATILE might be more intuitive (similar to the > proposed MADV_VOLATILE). > > But naming is hard, just mentioning to share my thought :) Naming is hard, but *renaming* is annoying. I like droppable simply because that's what I've been calling it in my head. MAP_VOLATILE is fine with me though, and seems reasonable enough. So I'll name it that, and then please don't change your mind about it later so I won't have to rename everything again. :) Jason