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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767791547; bh=nH1lIKowpY71IyFBqdjo2R6v53N3f0jy/DRCKOUdr3Q=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=SMpNz00VTY3IuWA9a30byLgzg6Yh6ZcTskIv7FxF7xT2ePEReH5jjvCRfdAV+cLh5 LwAzR/q1D8c/FAIqW0CctIwkKCcYV6SSZp/DKqTOsxpizdy5ADaYtVVgm3hwilByhW 6Fz3VwIocRheTWtQhyXxMg7P7dM5WD9EXcnxEEM2eo9l7W6/S5Qms6cPOtnDtXX9J5 VQh0/DfofvY8PKQQYfwzzs3swf0Yk+8tqNOpKKvQo2PzBoOFcbTvvimJ+onwZYWKIb B/tUp3pqY5pcDKygMahUQ+grzc1hNfzFT5Q/CkPIpGCm/dXEEJTXTTNOlB67ZEwOPV 8nTNltf5UqWUw== From: Andreas Hindborg To: Peter Zijlstra Cc: Alice Ryhl , Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?Q?Bj=C3=B6rn?= Roy Baron , Benno Lossin , Trevor Gross , Danilo Krummrich , Alexandre Courbot , Will Deacon , Mark Rutland , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Nicolas Schier , Andrew Morton , Uladzislau Rezki , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, linux-mm@kvack.org, nouveau@lists.freedesktop.org, Matthew Maurer Subject: Re: [PATCH 0/4] Inline helpers into Rust without full LTO In-Reply-To: <20260107123528.GF2393663@noisy.programming.kicks-ass.net> References: <20251202-inline-helpers-v1-0-879dae33a66a@google.com> <87y0m9har9.fsf@t14s.mail-host-address-is-not-set> <20260107123528.GF2393663@noisy.programming.kicks-ass.net> Date: Wed, 07 Jan 2026 14:12:10 +0100 Message-ID: <87sechh8id.fsf@t14s.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Rspamd-Queue-Id: 8A8FA18000B X-Rspamd-Server: rspam10 X-Stat-Signature: 4h7sbrfrf33e17y69st5sa6wrd5wzerd X-HE-Tag: 1767791548-324564 X-HE-Meta: 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 vev2Z8ub 6FcB5xjbJINjsgNkdehRJiD+R4MWkTmiPetxvi5dDof2EgXLZ6f9q+dWgt8kSn6GArRSftikp4JKqYQGStME23ETEdc6Ad0fSbMxKzGedg8AH62YWCu5QX896AZh6IdK9a/KuJyL11L7y5FuV6zAAbX2NepVeR64ZKDSGbIzrmTWtLjYey8kVcsqQteSG5qPuzNPEmoY2rHzk8fet2DzXI5snb1Co2DIFjdsrqhTak5V/rlseUqH9CdxHCzMQSIbPLAEcXjfPEvm63cMqzWOSvlCFFWaHZ4qcfxyP4HQD0YGm8+SSVk32hnn0TYtGoG3HXkHXsGQ5XpsPg77u31O1qJU0yA== 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: "Peter Zijlstra" writes: > On Wed, Jan 07, 2026 at 01:23:38PM +0100, Andreas Hindborg wrote: >> Hi Alice, >> >> Alice Ryhl writes: >> >> > Currently the only way for Rust code to call a static inline function is >> > to go through a helper in rust/helpers/. This introduces performance >> > costs due to additional function calls and also clutters backtraces and >> > flame graphs with helper symbols. >> > >> > To get rid of these helper symbols, provide functionality to inline >> > helpers into Rust using llvm-link. This option complements full LTO, by >> > being much cheaper and avoiding incompatibility with BTF. >> > >> > I ran a microbenchmark showing the benefit of this. All the benchmark >> > does is call refcount_inc() in a loop. This was chosen since refcounting >> > is quite hot in Binder. The results are that Rust spends 6.35 ns per >> > call vs 5.73 ns per call in C. When enabling this option, the two >> > languages become equally fast, and disassembly confirms the exact same >> > machine code is used (in particular there is no call to >> > rust_helper_refcount_inc). Benchmarking Binder also results in an >> > improvement from this change. >> > >> > This patch is complementary to: >> > https://lore.kernel.org/all/20251202-define-rust-helper-v1-0-a2e13cbc17a6@google.com/ >> > >> > Signed-off-by: Alice Ryhl >> >> I get the following modpost errors when building with this applied on top >> of v6.19-rc4: >> >> ERROR: modpost: "__SCK__WARN_trap" [drivers/gpu/drm/nova/nova.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [drivers/gpu/nova-core/nova_core.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [drivers/block/rnull/rnull_mod.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_minimal.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_misc_device.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_print.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_dma.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_driver_pci.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_driver_platform.ko] undefined! >> ERROR: modpost: "__SCK__WARN_trap" [samples/rust/rust_driver_faux.ko] undefined! > > Looks like it used the wrong static_call_mod() version, was MODULE > defined? CONFIG_MODULES=y, yes I built without the patch first, then applied the series, enabled the option via menuconfig and ran the build. I thought maybe some dependency check is messed up so I retried the build from a clean state. Same result. Best regards, Andreas Hindborg