On Wed, Mar 12, 2025 at 06:17:23PM +0800, I Hsin Cheng wrote: > Currenyly 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 100 bytes. > > $ ./scripts/bloat-o-meter vmlinux_old vmlinux_new > add/remove: 0/8 grow/shrink: 0/0 up/down: 0/-100 (-100) > Function old new delta > _RNvXs_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB4_5GuardNtNtCsdaXADs8PRFB_4core7default7Default7default 9 - -9 > _RNvXs0_NtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB5_5GuardNtNtNtCsdaXADs8PRFB_4core3ops4drop4Drop4drop 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__RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard6unlock 16 - -16 > __pfx__RNvMNtNtCsaYBeKL739Xz_6kernel4sync3rcuNtB2_5Guard3new 16 - -16 > Total: Before=23385830, After=23385730, chg -0.00% > > Link: https://github.com/Rust-for-Linux/linux/issues/1145 > Signed-off-by: I Hsin Cheng <richard120310@xxxxxxxxx> > --- > rust/kernel/sync/rcu.rs | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/rust/kernel/sync/rcu.rs b/rust/kernel/sync/rcu.rs > index b51d9150ffe2..26df2a6cb09f 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() }; Reviewed-by: Joel Fernandes <joelagnelf@xxxxxxxxxx> If no objections, I can queue it for 6.16 but let me know if Rust maintainers prefer to take it. thanks, - Joel
