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Message-ID: <20250423134344.3888205-6-bqe@google.com>
Date: Wed, 23 Apr 2025 13:43:36 +0000
From: Burak Emir <bqe@...gle.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Burak Emir <bqe@...gle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>,
Viresh Kumar <viresh.kumar@...aro.org>, Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
Gary Guo <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, rust-for-linux@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v7 4/5] rust: add find_bit_benchmark_rust module.
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.
Minor fix to the documentation of the corresponding C config
FIND_BIT_BENCHMARK, it was mentioning the wrong module name.
Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
Suggested-by: Yury Norov <yury.norov@...il.com>
Signed-off-by: Burak Emir <bqe@...gle.com>
---
MAINTAINERS | 1 +
lib/Kconfig.debug | 15 ++++-
lib/Makefile | 1 +
lib/find_bit_benchmark_rust.rs | 102 ++++++++++++++++++++++++++++++++
rust/bindings/bindings_helper.h | 1 +
rust/kernel/bitmap.rs | 14 +++++
6 files changed, 133 insertions(+), 1 deletion(-)
create mode 100644 lib/find_bit_benchmark_rust.rs
diff --git a/MAINTAINERS b/MAINTAINERS
index 7d107dc91390..d448b73c5934 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4140,6 +4140,7 @@ M: Alice Ryhl <aliceryhl@...gle.com>
M: Burak Emir <bqe@...gle.com>
R: Yury Norov <yury.norov@...il.com>
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..c1d4fc4a5f8f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2600,11 +2600,24 @@ config TEST_BPF
config FIND_BIT_BENCHMARK
tristate "Test find_bit functions"
help
- This builds the "test_find_bit" module that measure find_*_bit()
+ This builds the "find_bit_benchmark" module that measure find_*_bit()
functions performance.
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..9f4661baf70b
--- /dev/null
+++ b/lib/find_bit_benchmark_rust.rs
@@ -0,0 +1,102 @@
+// 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_find_next_bit(bitmap: &Bitmap) {
+ let mut time = Ktime::ktime_get();
+ let mut cnt = 0;
+ let mut i = 0;
+
+ loop {
+ cnt += 1;
+ if let Some(index) = bitmap.next_bit(i) {
+ i = index + 1;
+ if i == BITMAP_LEN {
+ break;
+ }
+ } else {
+ break;
+ }
+ }
+
+ time = Ktime::ktime_get() - time;
+ pr_err!("find_next_bit: {} ns, {} iterations\n", time.to_ns(), cnt);
+}
+
+fn test_find_next_zero_bit(bitmap: &Bitmap) {
+ let mut time = Ktime::ktime_get();
+ let mut cnt = 0;
+ let mut i = 0;
+ loop {
+ cnt += 1;
+ if let Some(index) = bitmap.next_zero_bit(i) {
+ i = index + 1;
+ if i == BITMAP_LEN {
+ break;
+ }
+ } else {
+ break;
+ }
+ }
+ time = Ktime::ktime_get() - time;
+ pr_err!(
+ "find_next_zero_bit: {} ns, {} 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_find_next_bit(&bitmap);
+ test_find_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_find_next_bit(&bitmap);
+ test_find_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: ["Rust for Linux Contributors"],
+ description: "Module with benchmark for bitmap code!",
+ 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 79ddbef2b028..5d2f6978ee6e 100644
--- a/rust/kernel/bitmap.rs
+++ b/rust/kernel/bitmap.rs
@@ -106,6 +106,20 @@ 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,
+ );
+ }
+ }
+
/// Returns a mutable raw pointer to the backing [`Bitmap`].
#[inline]
fn as_mut_ptr(&mut self) -> *mut usize {
--
2.49.0.805.g082f7c87e0-goog
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