Commit 38cc91db authored by Burak Emir's avatar Burak Emir Committed by Yury Norov (NVIDIA)
Browse files

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.

The sample output from the benchmark, both C and Rust version:

find_bit_benchmark.c output:
```
Start testing find_bit() with random-filled bitmap
[  438.101937] find_next_bit:                  860188 ns, 163419 iterations
[  438.109471] find_next_zero_bit:             912342 ns, 164262 iterations
[  438.116820] find_last_bit:                  726003 ns, 163419 iterations
[  438.130509] find_nth_bit:                  7056993 ns,  16269 iterations
[  438.139099] find_first_bit:                1963272 ns,  16270 iterations
[  438.173043] find_first_and_bit:           27314224 ns,  32654 iterations
[  438.180065] find_next_and_bit:              398752 ns,  73705 iterations
[  438.186689]
               Start testing find_bit() with sparse bitmap
[  438.193375] find_next_bit:                    9675 ns,    656 iterations
[  438.201765] find_next_zero_bit:            1766136 ns, 327025 iterations
[  438.208429] find_last_bit:                    9017 ns,    656 iterations
[  438.217816] find_nth_bit:                  2749742 ns,    655 iterations
[  438.225168] find_first_bit:                 721799 ns,    656 iterations
[  438.231797] find_first_and_bit:               2819 ns,      1 iterations
[  438.238441] find_next_and_bit:                3159 ns,      1 iterations
```

find_bit_benchmark_rust.rs output:
```
[  451.182459] find_bit_benchmark_rust:
[  451.186688] Start testing find_bit() Rust with random-filled bitmap
[  451.194450] next_bit:                       777950 ns, 163644 iterations
[  451.201997] next_zero_bit:                  918889 ns, 164036 iterations
[  451.208642] Start testing find_bit() Rust with sparse bitmap
[  451.214300] next_bit:                         9181 ns,    654 iterations
[  451.222806] next_zero_bit:                 1855504 ns, 327026 iterations
```

Here are the results from 32 samples, with 95% confidence interval.
The microbenchmark was built with RUST_BITMAP_HARDENED=n and run on a
machine that did not execute other processes.

Random-filled bitmap:
+-----------+-------+-----------+--------------+-----------+-----------+
| Benchmark | Lang  | Mean (ms) | Std Dev (ms) | 95% CI Lo | 95% CI Hi |
+-----------+-------+-----------+--------------+-----------+-----------+
| find_bit/ | C     |    825.07 |        53.89 |    806.40 |    843.74 |
| next_bit  | Rust  |    870.91 |        46.29 |    854.88 |    886.95 |
+-----------+-------+-----------+--------------+-----------+-----------+
| find_zero/| C     |    933.56 |        56.34 |    914.04 |    953.08 |
| next_zero | Rust  |    945.85 |        60.44 |    924.91 |    966.79 |
+-----------+-------+-----------+--------------+-----------+-----------+

Rust appears 5.5% slower for next_bit, 1.3% slower for next_zero.

Sparse bitmap:
+-----------+-------+-----------+--------------+-----------+-----------+
| Benchmark | Lang  | Mean (ms) | Std Dev (ms) | 95% CI Lo | 95% CI Hi |
+-----------+-------+-----------+--------------+-----------+-----------+
| find_bit/ | C     |     13.17 |         6.21 |     11.01 |     15.32 |
| next_bit  | Rust  |     14.30 |         8.27 |     11.43 |     17.17 |
+-----------+-------+-----------+--------------+-----------+-----------+
| find_zero/| C     |   1859.31 |        82.30 |   1830.80 |   1887.83 |
| next_zero | Rust  |   1908.09 |       139.82 |   1859.65 |   1956.54 |
+-----------+-------+-----------+--------------+-----------+-----------+

Rust appears 8.5% slower for next_bit, 2.6% slower for next_zero.

In summary, taking the arithmetic mean of all slow-downs, we can say
the Rust API has a 4.5% slowdown.

Suggested-by: default avatarAlice Ryhl <aliceryhl@google.com>
Suggested-by: default avatarYury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: default avatarYury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarBurak Emir <bqe@google.com>
Signed-off-by: default avatarYury Norov (NVIDIA) <yury.norov@gmail.com>
parent 11eca92a

MAINTAINERS

+1 −0
Original line number Diff line number Diff line
@@ -4307,6 +4307,7 @@ M: Alice Ryhl <aliceryhl@google.com> 
M:	Burak Emir <bqe@google.com>

R:	Yury Norov <yury.norov@gmail.com>

S:	Maintained

F:	lib/find_bit_benchmark_rust.rs

F:	rust/kernel/bitmap.rs









BITOPS API
































lib/Kconfig.debug



+13
−0






























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@@ -2607,6 +2607,19 @@ config FIND_BIT_BENCHMARK

















	  If unsure, say N.



















config FIND_BIT_BENCHMARK_RUST









	tristate "Test find_bit functions in Rust"









	depends on 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
































lib/Makefile



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@@ -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
































lib/find_bit_benchmark_rust.rs
0 → 100644



+104
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// 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::BitmapVec;









use kernel::error::{code, Result};









use kernel::prelude::module;









use kernel::time::{Instant, Monotonic};









use kernel::ThisModule;









use kernel::{pr_cont, pr_err};



















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 Benchmark();



















fn test_next_bit(bitmap: &BitmapVec) {









    let time = Instant::<Monotonic>::now();









    let mut cnt = 0;









    let mut i = 0;



















    while let Some(index) = bitmap.next_bit(i) {









        cnt += 1;









        i = index + 1;









        // CONFIG_RUST_BITMAP_HARDENED enforces strict bounds.









        if i == BITMAP_LEN {









            break;









        }









    }



















    let delta = time.elapsed();









    pr_cont!(









        "\nnext_bit:           {:18} ns, {:6} iterations",









        delta.as_nanos(),









        cnt









    );









}



















fn test_next_zero_bit(bitmap: &BitmapVec) {









    let time = Instant::<Monotonic>::now();









    let mut cnt = 0;









    let mut i = 0;



















    while let Some(index) = bitmap.next_zero_bit(i) {









        cnt += 1;









        i = index + 1;









        // CONFIG_RUST_BITMAP_HARDENED enforces strict bounds.









        if i == BITMAP_LEN {









            break;









        }









    }



















    let delta = time.elapsed();









    pr_cont!(









        "\nnext_zero_bit:      {:18} ns, {:6} iterations",









        delta.as_nanos(),









        cnt









    );









}



















fn find_bit_test() {









    pr_err!("Benchmark");









    pr_cont!("\nStart testing find_bit() Rust with random-filled bitmap");



















    let mut bitmap = BitmapVec::new(BITMAP_LEN, GFP_KERNEL).expect("alloc bitmap failed");









    bitmap.fill_random();



















    test_next_bit(&bitmap);









    test_next_zero_bit(&bitmap);



















    pr_cont!("\nStart testing find_bit() Rust with sparse bitmap");



















    let mut bitmap = BitmapVec::new(BITMAP_LEN, GFP_KERNEL).expect("alloc sparse bitmap failed");









    let nbits = BITMAP_LEN / SPARSENESS;









    for _i in 0..nbits {









        // SAFETY: __get_random_u32_below is safe to call with any u32 argument.









        let bit =









            unsafe { bindings::__get_random_u32_below(BITMAP_LEN.try_into().unwrap()) as usize };









        bitmap.set_bit(bit);









    }



















    test_next_bit(&bitmap);









    test_next_zero_bit(&bitmap);









    pr_cont!("\n");









}



















impl kernel::Module for Benchmark {









    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: Benchmark,









    name: "find_bit_benchmark_rust",









    authors: ["Burak Emir <bqe@google.com>"],









    description: "Module with benchmark for bitmap Rust API",









    license: "GPL v2",









}
























rust/bindings/bindings_helper.h



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@@ -67,6 +67,7 @@







#include <linux/pm_opp.h>









#include <linux/poll.h>









#include <linux/property.h>









#include <linux/random.h>









#include <linux/refcount.h>









#include <linux/regulator/consumer.h>









#include <linux/sched.h>