From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f181.google.com (mail-yw1-f181.google.com [209.85.128.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83173225416; Mon, 2 Jun 2025 14:32:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748874729; cv=none; b=YxNxx91YMcNXL0QPs4gDJW4ydA8pML4VyV3EORmmVfa32aWgGeF9judF8SZICfNyI0eA0kAkGFiM57ZsXx0VBVqSh9HyCgARsvcr9KvNmV+DcWYN3wAuAVu0Uglgvdz6e4013Uoxdcw4C31c6O72nXVoEGGUaMs1idDTjmQ9N8s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748874729; c=relaxed/simple; bh=JjgelIi9j9GCQSIEGKvmRZSvuyAxEWY3S62qh+JqMbY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PfFD/x1Fuo6pbUB5bKBNT4s0o/N4VxJrLQjXQMC1SlolYT32BVFhnoCf2VQFqawECddhRU79GnjPNRpamX3iMbch88rBVQy3d/NWL7xEee3SlwDcpQIGpek3178gY/AhrurDna2JwnkPCdpU0uvvNPYY0X3M3RzLx5eucrYGJbs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=bFFIMN8c; arc=none smtp.client-ip=209.85.128.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bFFIMN8c" Received: by mail-yw1-f181.google.com with SMTP id 00721157ae682-70e2b601a6bso40815047b3.0; Mon, 02 Jun 2025 07:32:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1748874725; x=1749479525; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=EvOI7RA2dDXQpHeuo3oal0L8s5UNFy6d5TD1756oBPE=; b=bFFIMN8cFaXAVoq7PuiEjvMGSUC8fjsuhBLyk2hh8zcFWNkJmtty5Tx4ZtQ6/EX3Tn irjl2L180L3I4r4PccDxnDN9j9Mga97G34/qP/OpmS/D0Zd1rC7XjXZejKC8d9+Ydv/3 xrqdWptE1VgIdRN5z836VXkQcgC92w5QPe0c0NSDTVLEidWlGl5MGopzPZEXT0DPDOyT thzTnN72GMWuC5PQuC0pzjTxIV0wavGu9rBugmwZTFALc3pnrXowFqU32M4UpIvFUdwJ gukl+ltpn+e2Yc/G39tNxqEJh08mjt1csHe5qia82rIduBEolS2q1yH3rkP/BQl1ZK+G Pdrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748874725; x=1749479525; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=EvOI7RA2dDXQpHeuo3oal0L8s5UNFy6d5TD1756oBPE=; b=MLyaca9FspGSOz4+xzpTWSbQ+jR9ZziSOKjRCSiwIepdIUxKvYlhCAQhTnJtMRx/tk 7LjLni35nDRou4Y4yjWsi0FWbTXgFgQJ2dShS6yl6bHG8h4or9Z1Hfu2TVjV9WmlJ+JW HZpja14rFfphV0k/AX5BB05aBF0ufL3OXKo70gz7x9py7AeZgQFTCv0NPVoGs0qKii/2 fHblBA2iRRbZsLIZoUF3NODO5HbCRBauP70xyVpMTG+F1gERh7sQ3GGX3HoBFfI8zeV9 JkbydHXnb8rPPAuFSf4Q7hEUAu+hDHPwe5iP5glulten+3MXF1f3KC72koKxX0emzPTu v7ZA== X-Forwarded-Encrypted: i=1; AJvYcCVjiYd6XGxE9CX0YuYE7H6qEtyucTqpwdiCTbyGnYKM0jzE7xzKQbKwkl2ZC6HOY8tDOrftRSO+UNS1c3H/BWE=@vger.kernel.org, AJvYcCVxE/h4IRGGB4LNuCGoUSdVcxkwvPISgpUebsVBrLwFPTjwuppCOIm61s/rKIYdAW1oY9x81ypaqYmdwdyw@vger.kernel.org, AJvYcCWgFmWrX71F+SLljRd6P8F0aHL85z3+cDz8KMW7X9FckZdvmztyOTjXS8UKH/xil9Jpmjve2wxnTpNkbqArOqE=@vger.kernel.org X-Gm-Message-State: AOJu0Yy1nvpJLQyVWMxyOLuVaCWFcANvoiRQdw7fdEUS2Oi/6oTHceVa aF+5e0AAOgt/MoCiKnTkiuq44bz5gypa1aNBhVMa1cutgFWyZTwAp6T0eCVI9w== X-Gm-Gg: ASbGncvFzIe0SAJ/4NXXFvJcP5O4hqeeCKBxVsOL7p96a50BaPzY+y8bnI3SSM0U/cM DL4nYknpTM3WlYguy/77GTTTtqfJJgkNJrCbxJ+y+zWQ+UK25JUtjaty6C7ST2a5pQ3cVZHoG1u 1I3nNLV22Aj4l2C5hnWYE8yUDQr3pM9yWzuz20IDzqccpVLk3HJtLzsdUtA0awze7gslJW3HPIL Bs5xkwz91+OlaCxMFJj+oOkFrA5CKRqnMi01iuDf3HuRJMDNQhusd41u+uZ+Qbt/TvDR0njOVlN +c8EQE8JlJGJLdAu6XzvclzmFo6OsK2uARFNZl1BF7DOl46Ry00= X-Google-Smtp-Source: AGHT+IEiP3UnD9CaqHkwTnZlqJth0Q93VqoYBVl42epJPG08PU0mOHK5uHzLVo2wSEOf5kE0q2sTjw== X-Received: by 2002:a05:6a20:1583:b0:1f5:8754:324d with SMTP id adf61e73a8af0-21ad9529415mr20048304637.9.1748874714725; Mon, 02 Jun 2025 07:31:54 -0700 (PDT) Received: from localhost ([216.228.127.130]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b2eceb09afesm5669901a12.3.2025.06.02.07.31.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Jun 2025 07:31:53 -0700 (PDT) Date: Mon, 2 Jun 2025 10:31:51 -0400 From: Yury Norov To: Burak Emir Cc: Kees Cook , Rasmus Villemoes , Viresh Kumar , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , "Gustavo A . R . Silva" , Carlos LLama , Pekka Ristola , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v10 4/5] rust: add find_bit_benchmark_rust module. Message-ID: References: <20250602133653.1606388-1-bqe@google.com> <20250602133653.1606388-5-bqe@google.com> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250602133653.1606388-5-bqe@google.com> On Mon, Jun 02, 2025 at 01:36:45PM +0000, Burak Emir wrote: > 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_module: > [ 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: Alice Ryhl > Suggested-by: Yury Norov > Signed-off-by: Burak Emir > --- > MAINTAINERS | 1 + > lib/Kconfig.debug | 13 +++++ > lib/Makefile | 1 + > lib/find_bit_benchmark_rust.rs | 95 +++++++++++++++++++++++++++++++++ > rust/bindings/bindings_helper.h | 1 + > rust/kernel/bitmap.rs | 14 +++++ > 6 files changed, 125 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 > M: Burak Emir > R: Yury Norov > 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..d8ed53f35495 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" > + 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 > 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..468a2087f68c > --- /dev/null > +++ b/lib/find_bit_benchmark_rust.rs > @@ -0,0 +1,95 @@ > +// 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::prelude::module; > +use kernel::time::Ktime; > +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; Is there any simple mechanism to keep C and rust sizes synced? (If no, not a big deal to redefine them.) > + > +/// 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_cont!( > + "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_cont!( > + "next_zero_bit: {:18} ns, {:6} iterations\n", > + time.to_ns(), > + cnt > + ); > +} > + > +fn find_bit_test() { > + pr_err!("\n"); > + pr_cont!("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_cont!("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 { > + find_bit_test(); > + // Return error so test module can be inserted again without rmmod. > + Err(code::EINVAL) > + } > +} > + > +module! { > + type: FindBitBenchmarkModule, I think we agreed to have the type something less unique, like: Benchmark. > + name: "find_bit_benchmark_rust_module", What is the name policy for rust? Maybe a more human-readable name would work better here? All the above are nits. Please have my Reviewed-by: Yury Norov [NVIDIA] Thanks, Yury > + authors: ["Burak Emir "], > + 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 > #include > #include > +#include > #include > #include > #include > diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs > index 28c11e400d1e..9fefb2473099 100644 > --- a/rust/kernel/bitmap.rs > +++ b/rust/kernel/bitmap.rs > @@ -252,6 +252,20 @@ pub fn new(nbits: usize, flags: Flags) -> Result { > 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 { > -- > 2.49.0.1204.g71687c7c1d-goog