From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailgw.kylinos.cn (mailgw.kylinos.cn [124.126.103.232]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA5422566E9; Mon, 26 Jan 2026 06:14:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=124.126.103.232 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769408066; cv=none; b=iCxvtQGt9c4ROXeVfGst1LHLj7hToz14L0sWYs2zUsDSqSuIgdQJWyVC2NHS7+cBb3r9nmksR8vDPSYLrh0maOU0+mCrGJqG7CJM3Pavq8uEbEzfzYu/I6WQglfwxhr0UFLKjrG3tevJJXFlhForKv2j/mCa7b0XHpijyWfHzrc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769408066; c=relaxed/simple; bh=6xJe9WF3eviWzuNmox8j94NcRQKPqUbjmbof8DJWU98=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=m/96Q5mak6o52GKUO4swxAjgyx4V6CP8KTRI7TuWNt09eh+WxJlE7TWyt8KPTs9EpX9vGjgVIfFjcwX9g2W7R4vUdFi4Pj0RCZbEEiKuhybi4JF3Hkawm0FrKM9Nmc9+qGDaUwqCPrMdQ7SytnH6OoSlIG5ah5D1DY7yb4uJgwU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn; spf=pass smtp.mailfrom=kylinos.cn; arc=none smtp.client-ip=124.126.103.232 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kylinos.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kylinos.cn X-UUID: 3f1cce4cfa7e11f0b0f03b4cfa9209d1-20260126 X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.3.6,REQID:967e08eb-15e0-4632-bf90-ea894c8c5d44,IP:0,UR L:0,TC:0,Content:0,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTION:r elease,TS:0 X-CID-META: VersionHash:a9d874c,CLOUDID:8e5d8eb21336d9844e695e1d29f0d6ca,BulkI D:nil,BulkQuantity:0,Recheck:0,SF:80|81|82|83|102|898,TC:nil,Content:0|15| 50,EDM:-3,IP:nil,URL:0,File:nil,RT:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0 ,OSA:0,AV:0,LES:1,SPR:NO,DKR:0,DKP:0,BRR:0,BRE:0,ARC:0 X-CID-BVR: 2,SSN|SDN X-CID-BAS: 2,SSN|SDN,0,_ X-CID-FACTOR: TF_CID_SPAM_SNR X-CID-RHF: D41D8CD98F00B204E9800998ECF8427E X-UUID: 3f1cce4cfa7e11f0b0f03b4cfa9209d1-20260126 X-User: jiangfeng@kylinos.cn Received: from [10.42.12.56] [(10.44.16.150)] by mailgw.kylinos.cn (envelope-from ) (Generic MTA with TLSv1.3 TLS_AES_128_GCM_SHA256 128/128) with ESMTP id 744551173; Mon, 26 Jan 2026 14:14:18 +0800 Message-ID: Date: Mon, 26 Jan 2026 14:14:14 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 4/8] lib/string_kunit: add performance benchmark for strlen() To: Andy Shevchenko Cc: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, akpm@linux-foundation.org, kees@kernel.org, andy@kernel.org, ebiggers@kernel.org, martin.petersen@oracle.com, mingo@kernel.org, charlie@rivosinc.com, conor.dooley@microchip.com, samuel.holland@sifive.com, linus.walleij@linaro.org, nathan@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20260123085841.212468-1-jiangfeng@kylinos.cn> <20260123085841.212468-5-jiangfeng@kylinos.cn> Content-Language: en-US From: Feng Jiang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 2026/1/23 19:02, Andy Shevchenko wrote: > On Fri, Jan 23, 2026 at 04:58:37PM +0800, Feng Jiang wrote: >> Introduce a benchmarking framework to the string_kunit test suite to >> measure the execution efficiency of string functions. >> >> The implementation is inspired by crc_benchmark(), measuring throughput >> (MB/s) and latency (ns/call) across a range of string lengths. It >> includes a warm-up phase, disables preemption during measurement, and >> uses a fixed seed for reproducible results. >> >> This framework allows for comparing different implementations (e.g., >> generic C vs. architecture-optimized assembly) within the KUnit >> environment. >> >> Initially, provide a benchmark for strlen(). > > ... > >> +static void *alloc_max_bench_buffer(struct kunit *test, >> + const size_t *lens, size_t count, size_t *buf_len) >> +{ >> + size_t i, max_len = 0; >> + void *buf; > >> + for (i = 0; i < count; i++) { >> + if (max_len < lens[i]) >> + max_len = lens[i]; >> + } > > size_t max_len = 0; > void *buf; > > for (size_t i = 0; i < count; i++) > max_len = max(lens[i], max_len); > Agreed. I will simplify the loop and use max() as suggested. >> + /* Add space for NUL character */ >> + max_len += 1; >> + >> + buf = kunit_kzalloc(test, max_len, GFP_KERNEL); >> + if (!buf) >> + return NULL; >> + >> + if (buf_len) >> + *buf_len = max_len; >> + >> + return buf; >> +} > > ... > >> +#define STRING_BENCH(iters, func, ...) \ >> +({ \ >> + /* Volatile function pointer prevents dead code elimination */ \ >> + typeof(func) (* volatile __func) = (func); \ >> + size_t __bn_iters = (iters); \ >> + size_t __bn_warm_iters; \ > >> + size_t __bn_i; \ > > Define it inside for-loop:s. > Will do. >> + u64 __bn_t; \ >> + \ >> + __bn_warm_iters = max(__bn_iters / 10, 50U); \ >> + \ >> + for (__bn_i = 0; __bn_i < __bn_warm_iters; __bn_i++) \ >> + (void)__func(__VA_ARGS__); \ >> + \ >> + preempt_disable(); \ >> + __bn_t = ktime_get_ns(); \ >> + for (__bn_i = 0; __bn_i < __bn_iters; __bn_i++) \ >> + (void)__func(__VA_ARGS__); \ >> + __bn_t = ktime_get_ns() - __bn_t; \ >> + preempt_enable(); \ >> + __bn_t; \ >> +}) > > ... > >> +#define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ >> +do { \ >> + size_t buf_size, _bn_i, _bn_iters, _bn_size = 0; \ >> + u64 _bn_t, _bn_mbps = 0, _bn_lat = 0; \ >> + char *buf_name, *_bn_buf; \ > >> + if (!IS_ENABLED(CONFIG_STRING_KUNIT_BENCH)) \ >> + kunit_skip(test, "not enabled"); \ > > Hmm... Since it's a macro anyway, I think the old style is okay: > > > #if IS_ENABLED(CONFIG_STRING_KUNIT_BENCH) > #define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ > ... > #else > #define STRING_BENCH_BUF(test, buf_name, buf_size, func, ...) \ > kunit_skip(test, "not enabled"); \ > #endif > > But check it that it doesn't produce warnings in `make W=1` case. > Thanks. Using #if IS_ENABLED(...) to define the macro differently is cleaner. I will implement it this way and ensure it passes make W=1 without warnings >> + _bn_buf = alloc_max_bench_buffer(test, bench_lens, \ >> + ARRAY_SIZE(bench_lens), &_bn_size); \ >> + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, _bn_buf); \ >> + \ >> + fill_random_string(_bn_buf, _bn_size); \ >> + \ >> + for (_bn_i = 0; _bn_i < ARRAY_SIZE(bench_lens); _bn_i++) { \ >> + buf_size = bench_lens[_bn_i]; \ >> + buf_name = _bn_buf + _bn_size - buf_size - 1; \ >> + _bn_iters = STRING_BENCH_WORKLOAD / max(buf_size, 1U); \ >> + \ >> + _bn_t = STRING_BENCH(_bn_iters, func, ##__VA_ARGS__); \ >> + \ >> + if (_bn_t > 0) { \ >> + _bn_mbps = (u64)(buf_size) * _bn_iters * 1000; \ > > "KILO"? Or "(MEGA/KILO)"? I'm puzzled with this 1000 multiplier. > The 1000 factor converts bytes/ns to MB/s： (bytes/ns) * (10^9 ns/s) / (10^6 bytes/MB) In v5, I will replace it with (NSEC_PER_SEC / MEGA) to make the unit conversion explicit and avoid confusion. >> + _bn_mbps = div64_u64(_bn_mbps, _bn_t); \ >> + _bn_lat = div64_u64(_bn_t, _bn_iters); \ >> + } \ >> + kunit_info(test, "len=%zu: %llu MB/s (%llu ns/call)\n", \ >> + buf_size, _bn_mbps, _bn_lat); \ >> + } \ >> +} while (0) > Thanks again for your time and for the detailed review! -- With Best Regards, Feng Jiang