| Message ID | 20250319022640.970207-1-richard120310@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] rust: sync: rcu: Mark Guard methods as inline | expand |
On Wed, Mar 19, 2025 at 10:26:40AM +0800, I Hsin Cheng wrote: > Currently the implementation of "Guard" methods are basically wrappers > around rcu's function within kernel. Building the kernel with llvm > 18.1.8 on x86_64 machine will generate the following symbols: > > $ nm vmlinux | grep ' _R'.*Guard | rustfilt > ffffffff817b6c90 T <kernel::sync::rcu::Guard>::new > ffffffff817b6cb0 T <kernel::sync::rcu::Guard>::unlock > ffffffff817b6cd0 T <kernel::sync::rcu::Guard as core::ops::drop::Drop>::drop > ffffffff817b6c90 T <kernel::sync::rcu::Guard as core::default::Default>::default > > These Rust symbols are basically wrappers around functions > "rcu_read_lock" and "rcu_read_unlock". Marking them as inline can > reduce the generation of these symbols, and saves the size of code > generation for 132 bytes. > > $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new [..] I am queuing this version for 6.16, please in the future add all reviewed-by and acked-by tags on resubmissions. This time I added it. Also I fixed up the demanging to make the change log look less ugly, let me know if it doesn't look Ok. ------------8<------------- From: I Hsin Cheng <richard120310@gmail.com> Subject: [PATCH v2] rust: sync: rcu: Mark Guard methods as inline Currently the implementation of "Guard" methods are basically wrappers around rcu's function within kernel. Building the kernel with llvm 18.1.8 on x86_64 machine will generate the following symbols: $ nm vmlinux | grep ' _R'.*Guard | rustfilt ffffffff817b6c90 T <kernel::sync::rcu::Guard>::new ffffffff817b6cb0 T <kernel::sync::rcu::Guard>::unlock ffffffff817b6cd0 T <kernel::sync::rcu::Guard as core::ops::drop::Drop>::drop ffffffff817b6c90 T <kernel::sync::rcu::Guard as core::default::Default>::default These Rust symbols are basically wrappers around functions "rcu_read_lock" and "rcu_read_unlock". Marking them as inline can reduce the generation of these symbols, and saves the size of code generation for 132 bytes. $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new (Output is demangled for readability) add/remove: 0/10 grow/shrink: 0/1 up/down: 0/-132 (-132) Function old new delta rust_driver_pci::SampleDriver::probe 1041 1034 -7 kernel::sync::rcu::Guard::default 9 - -9 kernel::sync::rcu::Guard::drop 9 - -9 kernel::sync::rcu::read_lock 9 - -9 kernel::sync::rcu::Guard::unlock 9 - -9 kernel::sync::rcu::Guard::new 9 - -9 __pfx__kernel::sync::rcu::Guard::default 16 - -16 __pfx__kernel::sync::rcu::Guard::drop 16 - -16 __pfx__kernel::sync::rcu::read_lock 16 - -16 __pfx__kernel::sync::rcu::Guard::unlock 16 - -16 __pfx__kernel::sync::rcu::Guard::new 16 - -16 Total: Before=23365955, After=23365823, chg -0.00% Link: https://github.com/Rust-for-Linux/linux/issues/1145 Signed-off-by: I Hsin Cheng <richard120310@gmail.com> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com> Reviewed-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Charalampos Mitrodimas <charmitro@posteo.net> Acked-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com> --- rust/kernel/sync/rcu.rs | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs index b51d9150ffe2..a32bef6e490b 100644 --- a/rust/kernel/sync/rcu.rs +++ b/rust/kernel/sync/rcu.rs @@ -17,6 +17,7 @@ impl Guard { /// Acquires the RCU read side lock and returns a guard. + #[inline] pub fn new() -> Self { // SAFETY: An FFI call with no additional requirements. unsafe { bindings::rcu_read_lock() }; @@ -25,16 +26,19 @@ pub fn new() -> Self { } /// Explicitly releases the RCU read side lock. + #[inline] pub fn unlock(self) {} } impl Default for Guard { + #[inline] fn default() -> Self { Self::new() } } impl Drop for Guard { + #[inline] fn drop(&mut self) { // SAFETY: By the type invariants, the RCU read side is locked, so it is ok to unlock it. unsafe { bindings::rcu_read_unlock() }; @@ -42,6 +46,7 @@ fn drop(&mut self) { } /// Acquires the RCU read side lock. +#[inline] pub fn read_lock() -> Guard { Guard::new() }
diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs index b51d9150ffe2..a32bef6e490b 100644 --- a/rust/kernel/sync/rcu.rs +++ b/rust/kernel/sync/rcu.rs @@ -17,6 +17,7 @@ impl Guard { /// Acquires the RCU read side lock and returns a guard. + #[inline] pub fn new() -> Self { // SAFETY: An FFI call with no additional requirements. unsafe { bindings::rcu_read_lock() }; @@ -25,16 +26,19 @@ pub fn new() -> Self { } /// Explicitly releases the RCU read side lock. + #[inline] pub fn unlock(self) {} } impl Default for Guard { + #[inline] fn default() -> Self { Self::new() } } impl Drop for Guard { + #[inline] fn drop(&mut self) { // SAFETY: By the type invariants, the RCU read side is locked, so it is ok to unlock it. unsafe { bindings::rcu_read_unlock() }; @@ -42,6 +46,7 @@ fn drop(&mut self) { } /// Acquires the RCU read side lock. +#[inline] pub fn read_lock() -> Guard { Guard::new() }
Currently the implementation of "Guard" methods are basically wrappers around rcu's function within kernel. Building the kernel with llvm 18.1.8 on x86_64 machine will generate the following symbols: $ nm vmlinux | grep ' _R'.*Guard | rustfilt ffffffff817b6c90 T <kernel::sync::rcu::Guard>::new ffffffff817b6cb0 T <kernel::sync::rcu::Guard>::unlock ffffffff817b6cd0 T <kernel::sync::rcu::Guard as core::ops::drop::Drop>::drop ffffffff817b6c90 T <kernel::sync::rcu::Guard as core::default::Default>::default These Rust symbols are basically wrappers around functions "rcu_read_lock" and "rcu_read_unlock". Marking them as inline can reduce the generation of these symbols, and saves the size of code generation for 132 bytes. $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new add/remove: 0/10 grow/shrink: 0/1 up/down: 0/-132 (-132) Function old new delta _RNvXs1_Cs4gouIKNZ4iT_15rust_driver_pciNtB5_12SampleDriverNtNtCsaYBeKL739Xz_6kernel3pci6Driver5probe 1041 1034 -7 _RNvXs_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB4_5GuardNtNtCsdaXADs8PRFB_4core7default7Default7default 9 - -9 _RNvXs0_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB5_5GuardNtNtNtCsdaXADs8PRFB_4core3ops4drop4Drop4drop 9 - -9 _RNvNtNtCsaYBeKL739Xz_6kernel4sync3rcu9read_lock 9 - -9 _RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard6unlock 9 - -9 _RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard3new 9 - -9 __pfx__RNvXs_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB4_5GuardNtNtCsdaXADs8PRFB_4core7default7Default7default 16 - -16 __pfx__RNvXs0_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB5_5GuardNtNtNtCsdaXADs8PRFB_4core3ops4drop4Drop4drop 16 - -16 __pfx__RNvNtNtCsaYBeKL739Xz_6kernel4sync3rcu9read_lock 16 - -16 __pfx__RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard6unlock 16 - -16 __pfx__RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard3new 16 - -16 Total: Before=23365955, After=23365823, chg -0.00% Link: https://github.com/Rust-for-Linux/linux/issues/1145 Signed-off-by: I Hsin Cheng <richard120310@gmail.com> --- Changelog: v1 -> v2: - Mark read_lock() as inline as well - Fix typos --- rust/kernel/sync/rcu.rs | 5 +++++ 1 file changed, 5 insertions(+)