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Message-ID: <20250526150141.3407433-5-bqe@google.com>
Date: Mon, 26 May 2025 15:01:33 +0000
From: Burak Emir <bqe@...gle.com>
To: Yury Norov <yury.norov@...il.com>, Kees Cook <kees@...nel.org>
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>, "Gustavo A . R . Silva" <gustavoars@...nel.org>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: [PATCH v9 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.
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 | 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 <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..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 <bqe@...gle.com>"],
+ 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
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