From patchwork Thu Feb 15 08:14:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Henderson X-Patchwork-Id: 772878 Delivered-To: patch@linaro.org Received: by 2002:adf:9dc2:0:b0:33b:4db1:f5b3 with SMTP id q2csp713266wre; Thu, 15 Feb 2024 00:16:35 -0800 (PST) X-Forwarded-Encrypted: i=2; AJvYcCUwL7aIv2isY5zmChy6PFzL72Bmr3KHkHvc6DDB8SQmzbBnhFXbTlxBsjSZxCzXbugPaAGBzwRk7ytuiNgXT2dl X-Google-Smtp-Source: AGHT+IE0ymUOgYslZ1ylsS69s9fp61t80O8qqbwo+NL+KaCa1C+URZl7Zlml9cBGwAiQzNkQjMMQ X-Received: by 2002:a0c:9d43:0:b0:68f:11ce:7ad6 with SMTP id n3-20020a0c9d43000000b0068f11ce7ad6mr960772qvf.20.1707984995127; Thu, 15 Feb 2024 00:16:35 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1707984995; cv=none; d=google.com; s=arc-20160816; b=w0jvHnh0e0WNUR3MQL81joX0zKN0zcFilOHbOQgF6lPHr78A0/gQGCHdoo21JjGlE1 nJ81OvjIR7v9M0qHfWJ5eVVdS7Kubx32PQ3aKI+DLZo5ULM44y40IUzPUmn5IDZBzTlh 3ThB7aLF3brT+iLUkrPMelPovCuiJvxkSz4HnJWSoIRgStzvSJnnhZIBHclgu0nzNCJE WU4nrvEDdif+apc15t5goaPJ99GIW1yHpoJNTGif2Bk96C+kSz2+bXIHtiNXTjjt0hA/ +JWeA6GPx8i9AaSSluX8thBxYWDqHEbO8OQTPqVfLZ2gRIFX6B5qKcpljUDRJsrOOQaK qDtQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:list-subscribe:list-help:list-post:list-archive :list-unsubscribe:list-id:precedence:content-transfer-encoding :mime-version:references:in-reply-to:message-id:date:subject:cc:to :from:dkim-signature; bh=dXCRLUcCrBeHTOJN8WRLVbCeiDdcG1rvhb6HzJR+Pi4=; fh=bXD9UGo7d05OYjVg0qF2wA28p2gxs496M6ftxgeDKVY=; b=y+D5eI9ectoLKA6pKfCSEl2E1UQCHyeYWD2XkZYLgHu6F34QoGtoChA51+bEHNxYUx SCCsDSXApuJMgARv+cHn20gLQGV+Z1orfRV6VKeUTxP7p27MUncn76ltInz/7wHdAM1s 4F/ksgOj2TxhPzwvc/w8Na6EtUl+QttbfCkX0cpQQiA/YwkjYC0GW+880ijU1o1v/c8w myd9R6IZWW70OlLzr9VFwQOoDlxlWb7YpKIWLoIcS90RPK9v6Enlaadl/djNZJZogT+J qf3HsZXKxe0OGW609XZY+zGOD2VILbJTv5lwEAGd0n8iU5DxFMtFyg68eGfk1eVhtuJB Hr/Q==; dara=google.com ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b="fN/YWgu4"; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+patch=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from lists.gnu.org (lists.gnu.org. [209.51.188.17]) by mx.google.com with ESMTPS id fn11-20020ad45d6b000000b0068ca70ec311si966347qvb.167.2024.02.15.00.16.34 for (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 15 Feb 2024 00:16:35 -0800 (PST) Received-SPF: pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b="fN/YWgu4"; spf=pass (google.com: domain of qemu-devel-bounces+patch=linaro.org@nongnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom="qemu-devel-bounces+patch=linaro.org@nongnu.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1raWu9-0007iw-U3; Thu, 15 Feb 2024 03:15:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1raWtX-00076g-9n for qemu-devel@nongnu.org; Thu, 15 Feb 2024 03:14:59 -0500 Received: from mail-pg1-x52d.google.com ([2607:f8b0:4864:20::52d]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1raWtV-0001Ne-CU for qemu-devel@nongnu.org; Thu, 15 Feb 2024 03:14:59 -0500 Received: by mail-pg1-x52d.google.com with SMTP id 41be03b00d2f7-53fbf2c42bfso488195a12.3 for ; Thu, 15 Feb 2024 00:14:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1707984896; x=1708589696; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=dXCRLUcCrBeHTOJN8WRLVbCeiDdcG1rvhb6HzJR+Pi4=; b=fN/YWgu4I2uogIlX4DZDGhuCci0c2r3g076Fp/U8f/yy+1HZnu0S6G7JQ7ZxtkY64v ZGsCpbjyRpFrRW8qH50UatrUfjcVGZvyl0iQgb3uYlfTy9KQ2TuwX5W97NhguO9DT31I 6aI3nm//CMxpOkHH69OWK7CvlziPMOliTX/R7RXaa46K65NofHJzjN5BCAMDIKdaIqVh jPuJn7ALwi2rS5rPdmVvhUjay1tSCZtKPY4Gekg04Rz+c9W1maGWiKXSYObyai5aL7Lw HzMa2Km3rAQhMFsVluMeNCSxi4xFpJYcKh0NpgNt/EjXuCYCXbZbxlWB12kBcvyu0lKl tf4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707984896; x=1708589696; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=dXCRLUcCrBeHTOJN8WRLVbCeiDdcG1rvhb6HzJR+Pi4=; b=czfzXTCvINMkJ1BJc7gjJD6g3IyPxrjYcpyjdjN4klvhMcq/DMJyoUqeYXrbLFJjbT 7TrjikHw7cmjeS66OSHOq7mr40lC+a0Q9CK6IOiXqM7EEflzs4ZDktQXdnEVPN11HQjk gpEynIVeOYcZsVHn/KRAz5sZ05seFWLz2FoqG8SzPSuSYSCW+1B0fkZssF4tZwXtUM+N MdaufpL2bfHQ3oO36r+7tTf5gEWrBYHhuszEx2ZSqKYAfi7alGi14+1WZ22DJcoVVgGW nNck4zWIgMI7UWtj2meU2DVgEcc9DSRym09U9Awdvt3S3Yj1Qnf5htVx4dVk1u8dCyRW 0LQw== X-Gm-Message-State: AOJu0Yygc7TxkqkDgufih2J1Us3sUqSvvcRY7KpdR7S0VNXI/31pli+M 1jLkTbrdfu0s7CqOXsAJlowgnoeutTi9c7QzuQBOjIKEhIKBHJ/OWEPludIAjHhKNcy5X4jlVdZ h X-Received: by 2002:a05:6a20:a195:b0:19e:425e:ec56 with SMTP id r21-20020a056a20a19500b0019e425eec56mr980332pzk.24.1707984895996; Thu, 15 Feb 2024 00:14:55 -0800 (PST) Received: from stoup.. (173-197-098-125.biz.spectrum.com. [173.197.98.125]) by smtp.gmail.com with ESMTPSA id qc14-20020a17090b288e00b0029900404e11sm807755pjb.27.2024.02.15.00.14.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Feb 2024 00:14:55 -0800 (PST) From: Richard Henderson To: qemu-devel@nongnu.org Cc: amonakov@ispras.ru, mmromanov@ispras.ru Subject: [PATCH v4 03/10] util/bufferiszero: Reorganize for early test for acceleration Date: Wed, 14 Feb 2024 22:14:42 -1000 Message-Id: <20240215081449.848220-4-richard.henderson@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240215081449.848220-1-richard.henderson@linaro.org> References: <20240215081449.848220-1-richard.henderson@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::52d; envelope-from=richard.henderson@linaro.org; helo=mail-pg1-x52d.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patch=linaro.org@nongnu.org Sender: qemu-devel-bounces+patch=linaro.org@nongnu.org From: Alexander Monakov Test for length >= 256 inline, where is is often a constant. Before calling into the accelerated routine, sample three bytes from the buffer, which handles most non-zero buffers. Signed-off-by: Alexander Monakov Signed-off-by: Mikhail Romanov Message-Id: <20240206204809.9859-3-amonakov@ispras.ru> [rth: Use __builtin_constant_p and perform the sample out-of-line.] Signed-off-by: Richard Henderson --- include/qemu/cutils.h | 15 +++++++- util/bufferiszero.c | 89 ++++++++++++++++++------------------------- 2 files changed, 51 insertions(+), 53 deletions(-) diff --git a/include/qemu/cutils.h b/include/qemu/cutils.h index 92c927a6a3..36f8cfa0e9 100644 --- a/include/qemu/cutils.h +++ b/include/qemu/cutils.h @@ -187,9 +187,22 @@ char *freq_to_str(uint64_t freq_hz); /* used to print char* safely */ #define STR_OR_NULL(str) ((str) ? (str) : "null") -bool buffer_is_zero(const void *buf, size_t len); +/* + * Check if a buffer is all zeroes. + */ + +bool buffer_is_zero_ool(const void *vbuf, size_t len); +bool buffer_is_zero_ge256(const void *vbuf, size_t len); bool test_buffer_is_zero_next_accel(void); +#ifdef __OPTIMIZE__ +#define buffer_is_zero(B, L) \ + (__builtin_constant_p(L) && (size_t)(L) >= 256 \ + ? buffer_is_zero_ge256(B, L) : buffer_is_zero_ool(B, L)) +#else +#define buffer_is_zero buffer_is_zero_ool +#endif + /* * Implementation of ULEB128 (http://en.wikipedia.org/wiki/LEB128) * Input is limited to 14-bit numbers diff --git a/util/bufferiszero.c b/util/bufferiszero.c index 641d5f9b9e..38527f2467 100644 --- a/util/bufferiszero.c +++ b/util/bufferiszero.c @@ -26,8 +26,9 @@ #include "qemu/bswap.h" #include "host/cpuinfo.h" -static bool -buffer_zero_int(const void *buf, size_t len) +static bool (*buffer_is_zero_accel)(const void *, size_t); + +static bool buffer_is_zero_integer(const void *buf, size_t len) { if (unlikely(len < 8)) { /* For a very small buffer, simply accumulate all the bytes. */ @@ -128,60 +129,38 @@ buffer_zero_avx2(const void *buf, size_t len) } #endif /* CONFIG_AVX2_OPT */ -/* - * Make sure that these variables are appropriately initialized when - * SSE2 is enabled on the compiler command-line, but the compiler is - * too old to support CONFIG_AVX2_OPT. - */ -#if defined(CONFIG_AVX2_OPT) -# define INIT_USED 0 -# define INIT_LENGTH 0 -# define INIT_ACCEL buffer_zero_int -#else -# ifndef __SSE2__ -# error "ISA selection confusion" -# endif -# define INIT_USED CPUINFO_SSE2 -# define INIT_LENGTH 64 -# define INIT_ACCEL buffer_zero_sse2 -#endif - -static unsigned used_accel = INIT_USED; -static unsigned length_to_accel = INIT_LENGTH; -static bool (*buffer_accel)(const void *, size_t) = INIT_ACCEL; - static unsigned __attribute__((noinline)) select_accel_cpuinfo(unsigned info) { /* Array is sorted in order of algorithm preference. */ static const struct { unsigned bit; - unsigned len; bool (*fn)(const void *, size_t); } all[] = { #ifdef CONFIG_AVX2_OPT - { CPUINFO_AVX2, 128, buffer_zero_avx2 }, + { CPUINFO_AVX2, buffer_zero_avx2 }, #endif - { CPUINFO_SSE2, 64, buffer_zero_sse2 }, - { CPUINFO_ALWAYS, 0, buffer_zero_int }, + { CPUINFO_SSE2, buffer_zero_sse2 }, + { CPUINFO_ALWAYS, buffer_is_zero_integer }, }; for (unsigned i = 0; i < ARRAY_SIZE(all); ++i) { if (info & all[i].bit) { - length_to_accel = all[i].len; - buffer_accel = all[i].fn; + buffer_is_zero_accel = all[i].fn; return all[i].bit; } } return 0; } -#if defined(CONFIG_AVX2_OPT) +static unsigned used_accel; + static void __attribute__((constructor)) init_accel(void) { used_accel = select_accel_cpuinfo(cpuinfo_init()); } -#endif /* CONFIG_AVX2_OPT */ + +#define INIT_ACCEL NULL bool test_buffer_is_zero_next_accel(void) { @@ -194,36 +173,42 @@ bool test_buffer_is_zero_next_accel(void) used_accel |= used; return used; } - -static bool select_accel_fn(const void *buf, size_t len) -{ - if (likely(len >= length_to_accel)) { - return buffer_accel(buf, len); - } - return buffer_zero_int(buf, len); -} - #else -#define select_accel_fn buffer_zero_int bool test_buffer_is_zero_next_accel(void) { return false; } + +#define INIT_ACCEL buffer_is_zero_integer #endif -/* - * Checks if a buffer is all zeroes - */ -bool buffer_is_zero(const void *buf, size_t len) +static bool (*buffer_is_zero_accel)(const void *, size_t) = INIT_ACCEL; + +static inline bool buffer_is_zero_sample3(const char *buf, size_t len) +{ + return (buf[0] | buf[len - 1] | buf[len / 2]) == 0; +} + +bool buffer_is_zero_ool(const void *buf, size_t len) { if (unlikely(len == 0)) { return true; } + if (!buffer_is_zero_sample3(buf, len)) { + return false; + } + /* All bytes are covered for any len <= 3. */ + if (unlikely(len <= 3)) { + return true; + } - /* Fetch the beginning of the buffer while we select the accelerator. */ - __builtin_prefetch(buf); - - /* Use an optimized zero check if possible. Note that this also - includes a check for an unrolled loop over 64-bit integers. */ - return select_accel_fn(buf, len); + if (likely(len >= 256)) { + return buffer_is_zero_accel(buf, len); + } + return buffer_is_zero_integer(buf, len); +} + +bool buffer_is_zero_ge256(const void *buf, size_t len) +{ + return buffer_is_zero_sample3(buf, len) && buffer_is_zero_accel(buf, len); }