Microbenchmark protected by a config FIND_BIT_BENCHMARK_RUST, following `find_bit_benchmark.c` but testing the Rust Bitmap API.
We add a fill_random() method protected by the config in order to maintain the abstraction. Suggested-by: Alice Ryhl <[email protected]> Suggested-by: Yury Norov <[email protected]> Signed-off-by: Burak Emir <[email protected]> --- MAINTAINERS | 1 + lib/Kconfig.debug | 13 +++++ lib/Makefile | 1 + lib/find_bit_benchmark_rust.rs | 94 +++++++++++++++++++++++++++++++++ rust/bindings/bindings_helper.h | 1 + rust/kernel/bitmap.rs | 14 +++++ 6 files changed, 124 insertions(+) create mode 100644 lib/find_bit_benchmark_rust.rs diff --git a/MAINTAINERS b/MAINTAINERS index 565eaa015d9e..943d85ed1876 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4132,6 +4132,7 @@ M: Alice Ryhl <[email protected]> M: Burak Emir <[email protected]> R: Yury Norov <[email protected]> S: Maintained +F: lib/find_bit_benchmark_rust.rs F: rust/kernel/bitmap.rs BITOPS API diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index f9051ab610d5..37a07559243e 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2605,6 +2605,19 @@ config FIND_BIT_BENCHMARK If unsure, say N. +config FIND_BIT_BENCHMARK_RUST + tristate "Test find_bit functions in Rust" + help + This builds the "find_bit_benchmark_rust" module. It is a micro + benchmark that measures the performance of Rust functions that + correspond to the find_*_bit() operations in C. It follows the + FIND_BIT_BENCHMARK closely but will in general not yield same + numbers due to extra bounds checks and overhead of foreign + function calls. + + If unsure, say N. + + config TEST_FIRMWARE tristate "Test firmware loading via userspace interface" depends on FW_LOADER diff --git a/lib/Makefile b/lib/Makefile index f07b24ce1b3f..99e49a8f5bf8 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -62,6 +62,7 @@ obj-y += hexdump.o obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o obj-y += kstrtox.o obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o +obj-$(CONFIG_FIND_BIT_BENCHMARK_RUST) += find_bit_benchmark_rust.o obj-$(CONFIG_TEST_BPF) += test_bpf.o test_dhry-objs := dhry_1.o dhry_2.o dhry_run.o obj-$(CONFIG_TEST_DHRY) += test_dhry.o diff --git a/lib/find_bit_benchmark_rust.rs b/lib/find_bit_benchmark_rust.rs new file mode 100644 index 000000000000..4966bfa497f1 --- /dev/null +++ b/lib/find_bit_benchmark_rust.rs @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0 +//! Benchmark for find_bit-like methods in Bitmap Rust API. + +use kernel::alloc::flags::GFP_KERNEL; +use kernel::bindings; +use kernel::bitmap::Bitmap; +use kernel::error::{code, Result}; +use kernel::pr_err; +use kernel::prelude::module; +use kernel::time::Ktime; +use kernel::ThisModule; + +const BITMAP_LEN: usize = 4096 * 8 * 10; +// Reciprocal of the fraction of bits that are set in sparse bitmap. +const SPARSENESS: usize = 500; + +/// Test module that benchmarks performance of traversing bitmaps. +struct FindBitBenchmarkModule(); + +fn test_next_bit(bitmap: &Bitmap) { + let mut time = Ktime::ktime_get(); + let mut cnt = 0; + let mut i = 0; + + while let Some(index) = bitmap.next_bit(i) { + cnt += 1; + i = index + 1; + } + + time = Ktime::ktime_get() - time; + pr_err!( + "next_bit: {:18} ns, {:6} iterations\n", + time.to_ns(), + cnt + ); +} + +fn test_next_zero_bit(bitmap: &Bitmap) { + let mut time = Ktime::ktime_get(); + let mut cnt = 0; + let mut i = 0; + + while let Some(index) = bitmap.next_zero_bit(i) { + cnt += 1; + i = index + 1; + } + + time = Ktime::ktime_get() - time; + pr_err!( + "next_zero_bit: {:18} ns, {:6} iterations\n", + time.to_ns(), + cnt + ); +} + +fn find_bit_test() { + pr_err!("Start testing find_bit() Rust with random-filled bitmap\n"); + + let mut bitmap = Bitmap::new(BITMAP_LEN, GFP_KERNEL).expect("alloc bitmap failed"); + bitmap.fill_random(); + + test_next_bit(&bitmap); + test_next_zero_bit(&bitmap); + + pr_err!("Start testing find_bit() Rust with sparse bitmap\n"); + + let mut bitmap = Bitmap::new(BITMAP_LEN, GFP_KERNEL).expect("alloc sparse bitmap failed"); + let nbits = BITMAP_LEN / SPARSENESS; + for _i in 0..nbits { + // SAFETY: BITMAP_LEN fits in 32 bits. + let bit: usize = + unsafe { bindings::__get_random_u32_below(BITMAP_LEN.try_into().unwrap()) as _ }; + bitmap.set_bit(bit); + } + + test_next_bit(&bitmap); + test_next_zero_bit(&bitmap); +} + +impl kernel::Module for FindBitBenchmarkModule { + fn init(_module: &'static ThisModule) -> Result<Self> { + find_bit_test(); + // Return error so test module can be inserted again without rmmod. + Err(code::EINVAL) + } +} + +module! { + type: FindBitBenchmarkModule, + name: "find_bit_benchmark_rust_module", + authors: ["Burak Emir <[email protected]>"], + description: "Module with benchmark for bitmap Rust API", + license: "GPL v2", +} diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index b6bf3b039c1b..f6ca7f1dd08b 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -31,6 +31,7 @@ #include <linux/platform_device.h> #include <linux/poll.h> #include <linux/property.h> +#include <linux/random.h> #include <linux/refcount.h> #include <linux/sched.h> #include <linux/security.h> diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs index a6edd4889518..fa5fef0b6acd 100644 --- a/rust/kernel/bitmap.rs +++ b/rust/kernel/bitmap.rs @@ -232,6 +232,20 @@ pub fn new(nbits: usize, flags: Flags) -> Result<Self, AllocError> { pub fn len(&self) -> usize { self.nbits } + + /// Fills this `Bitmap` with random bits. + #[cfg(CONFIG_FIND_BIT_BENCHMARK_RUST)] + pub fn fill_random(&mut self) { + // SAFETY: `self.as_mut_ptr` points to either an array of the + // appropriate length or one usize. + unsafe { + bindings::get_random_bytes( + self.as_mut_ptr() as *mut ffi::c_void, + usize::div_ceil(self.nbits, bindings::BITS_PER_LONG as usize) + * bindings::BITS_PER_LONG as usize, + ); + } + } } impl CBitmap { -- 2.49.0.1151.ga128411c76-goog
