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Tue, 26 Nov 2024 13:51:24 -0800 (PST) MIME-Version: 1.0 References: <20241122-vma-v9-0-7127bfcdd54e@google.com> <20241122-vma-v9-4-7127bfcdd54e@google.com> In-Reply-To: <20241122-vma-v9-4-7127bfcdd54e@google.com> From: Jann Horn Date: Tue, 26 Nov 2024 22:50:48 +0100 Message-ID: Subject: Re: [PATCH v9 4/8] mm: rust: add lock_vma_under_rcu To: Alice Ryhl Cc: Miguel Ojeda , Matthew Wilcox , Lorenzo Stoakes , Vlastimil Babka , John Hubbard , "Liam R. Howlett" , Andrew Morton , Greg Kroah-Hartman , Arnd Bergmann , Christian Brauner , Suren Baghdasaryan , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , linux-kernel@vger.kernel.org, linux-mm@kvack.org, rust-for-linux@vger.kernel.org, Andreas Hindborg Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5EC621C0007 X-Stat-Signature: og8r3rx47fen49asgp5sc49myy6r913e X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1732657884-392480 X-HE-Meta: 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 7Jq/3RVH TpOQ+y53XUj5uVeUV/JIuUVo7wU0qXgU5Btm9dp4sQkRmz3Sxvp6PZhcsA2lOZ2v21diaSBKJB9T9S2rqmSdrU98dX6pZ+tDFTCFfPo/I7HG9fgLcLM6wBdw99bZXgwb/VUC0LvDukZFq+OODJgnZ3YA3qv7aPp6n+SMUa+KAKquOsSPctFzdEBfDmDf1EqSdB1vW4REON4RF4M4Gd4S35+iKSzbPabSkGMkzY9lP9hVT/Zp0NjDXsAybM1qdHwIcCV24U9kPmWUVEkt3qpnVgtXXtsJJr78UsnIbOxoV+gk0MTBQ2PcTg5S+Axy9Da5FhiZi8JIKYcSjB6mhV2wfwqqXP4DmCMH0soTKtID0XniPwl8= 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 Fri, Nov 22, 2024 at 4:41=E2=80=AFPM Alice Ryhl w= rote: > Currently, the binder driver always uses the mmap lock to make changes > to its vma. Because the mmap lock is global to the process, this can > involve significant contention. However, the kernel has a feature called > per-vma locks, which can significantly reduce contention. For example, > you can take a vma lock in parallel with an mmap write lock. This is > important because contention on the mmap lock has been a long-term > recurring challenge for the Binder driver. > > This patch introduces support for using `lock_vma_under_rcu` from Rust. > The Rust Binder driver will be able to use this to reduce contention on > the mmap lock. > > Acked-by: Lorenzo Stoakes (for mm bits) > Signed-off-by: Alice Ryhl Reviewed-by: Jann Horn