From patchwork Mon May 9 17:17:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Noah Goldstein X-Patchwork-Id: 53678 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id A17DB3857370 for ; Mon, 9 May 2022 17:21:26 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A17DB3857370 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1652116886; bh=8XXwIyepiRR89xe1+sD2xpOrLwdE6RLLzFY6bSfdgDg=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=C4xCY8ugYyvFsPypSoZdKo5oLseIchAgr8O2eJM7bg716KykJTOscLtH21NsCa2Iv cIGM/oup6DssAp57da/Cw9teGH3W+ICLDKdh2+YPE/P55UzDM+WpHwggg+WrXzGt53 sFhS+bp4236Wiwd3jRM9+S91DJ+PGeVB/LnC5CDE= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-il1-x12d.google.com (mail-il1-x12d.google.com [IPv6:2607:f8b0:4864:20::12d]) by sourceware.org (Postfix) with ESMTPS id 8DA38384B07E for ; Mon, 9 May 2022 17:18:02 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 8DA38384B07E Received: by mail-il1-x12d.google.com with SMTP id r17so9744788iln.9 for ; Mon, 09 May 2022 10:18:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=8XXwIyepiRR89xe1+sD2xpOrLwdE6RLLzFY6bSfdgDg=; b=iyjgiZCMwiiLNxqPLGYzxTIAKG0JmW/EK6ozB1+nDz8/8xbO7wpno7wu17mLg5uwRQ F/wIwQr/0RJL4K5YRamDh69wwGawY/CKqq4ywapHg8jQgrHpYr6Igo36oaKgXMS53Zdn OJF6y74dPXnsLLXPD4s0z9L8bUwcDFG92WyTWWe7B5axssjhhpyX4C5gFs+7YyoVzsr2 5c3pMv+N2Upi9zcU1NBbiuIdXZueOnEGY4ShVw/o4GstmkwpPJg5k7XrvmxWri9hxHPz 7mbY0zoJcVBlmZuG+ZXMQRb8S0GcwwLxJYC+owvE1m3JBAhViKWNGcLJa30DiKOMrKuA p2vw== X-Gm-Message-State: AOAM5320cTcVKkE02lC9H+n0Vla/nOJmJ/9CMHHbkKO0NjhobJ3QUbCy BbNM2aBRBCc/tIdkCfmCRhaNmocZwzg= X-Google-Smtp-Source: ABdhPJx4FY/nkb7gyPnR62VUWjWbLFLXBrUsR3aruD4OHp0qaLXDVTXEHWJeNHF99ddsmm/2KkQovg== X-Received: by 2002:a92:1e09:0:b0:2c6:304e:61fa with SMTP id e9-20020a921e09000000b002c6304e61famr7732559ile.211.1652116681661; Mon, 09 May 2022 10:18:01 -0700 (PDT) Received: from noah-tgl.. ([2600:1008:b051:8883:74c9:7302:c07a:dbde]) by smtp.gmail.com with ESMTPSA id r6-20020a056638044600b0032b3a781756sm3734491jap.26.2022.05.09.10.18.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 May 2022 10:18:01 -0700 (PDT) To: libc-alpha@sourceware.org Subject: [PATCH v5 5/6] nss: Optimize nss_hash in nss_hash.c Date: Mon, 9 May 2022 12:17:46 -0500 Message-Id: <20220509171747.4153703-5-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220509171747.4153703-1-goldstein.w.n@gmail.com> References: <20220414041231.926415-1-goldstein.w.n@gmail.com> <20220509171747.4153703-1-goldstein.w.n@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, LIKELY_SPAM_BODY, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Noah Goldstein via Libc-alpha From: Noah Goldstein Reply-To: Noah Goldstein Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" The prior unrolling didn't really do much as it left the dependency chain between iterations. Unrolled the loop for 4 so 4x multiplies could be pipelined in out-of-order machines. Results for __nss_hash Benchmarked on Tigerlake: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz Time as Geometric Mean of N=25 runs Geometric of all benchmark New / Old: 0.845 type, length, New Time, Old Time, New Time / Old Time fixed, 0, 4.019, 3.729, 1.078 fixed, 1, 4.95, 5.707, 0.867 fixed, 2, 5.152, 5.657, 0.911 fixed, 3, 4.641, 5.721, 0.811 fixed, 4, 5.551, 5.81, 0.955 fixed, 5, 6.525, 6.552, 0.996 fixed, 6, 6.711, 6.561, 1.023 fixed, 7, 6.715, 6.767, 0.992 fixed, 8, 7.874, 7.915, 0.995 fixed, 9, 8.888, 9.767, 0.91 fixed, 10, 8.959, 9.762, 0.918 fixed, 11, 9.188, 9.987, 0.92 fixed, 12, 9.708, 10.618, 0.914 fixed, 13, 10.393, 11.14, 0.933 fixed, 14, 10.628, 12.097, 0.879 fixed, 15, 10.982, 12.965, 0.847 fixed, 16, 11.851, 14.429, 0.821 fixed, 32, 24.334, 34.414, 0.707 fixed, 64, 55.618, 86.688, 0.642 fixed, 128, 118.261, 224.36, 0.527 fixed, 256, 256.183, 538.629, 0.476 random, 2, 11.194, 11.556, 0.969 random, 4, 17.516, 17.205, 1.018 random, 8, 23.501, 20.985, 1.12 random, 16, 28.131, 29.212, 0.963 random, 32, 35.436, 38.662, 0.917 random, 64, 45.74, 58.868, 0.777 random, 128, 75.394, 121.963, 0.618 random, 256, 139.524, 260.726, 0.535 --- nss/nss_hash.c | 79 +++++++++++++++++++++++++++----------------------- 1 file changed, 42 insertions(+), 37 deletions(-) diff --git a/nss/nss_hash.c b/nss/nss_hash.c index 27a348ea9b..c6a375f386 100644 --- a/nss/nss_hash.c +++ b/nss/nss_hash.c @@ -19,58 +19,63 @@ /* This is from libc/db/hash/hash_func.c, hash3 is static there */ /* - * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte + * This is INCREDIBLY ugly, but fast. We break the string up into 4 byte * units. On the first time through the loop we get the "leftover bytes" - * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle - * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If - * this routine is heavily used enough, it's worth the ugly coding. + * (len % 4). On every other iteration, we perform a 4x unrolled version + * HASHC. Further unrolling does not appear to help. * * OZ's original sdbm hash */ uint32_t __nss_hash (const void *keyarg, size_t len) { + enum + { + HASH_CONST_P0 = 1, /* (uint32_t)(65599 ^ 0). */ + HASH_CONST_P1 = 65599, /* (uint32_t)(65599 ^ 1). */ + HASH_CONST_P2 = 8261505, /* (uint32_t)(65599 ^ 2). */ + HASH_CONST_P3 = 780587199, /* (uint32_t)(65599 ^ 3). */ + HASH_CONST_P4 = 1139564289 /* (uint32_t)(65599 ^ 4). */ + }; + const unsigned char *key; - size_t loop; uint32_t h; -#define HASHC h = *key++ + 65599 * h +#define HASHC h = *key++ + HASH_CONST_P1 * h h = 0; key = keyarg; if (len > 0) { - loop = (len + 8 - 1) >> 3; - switch (len & (8 - 1)) - { - case 0: - do - { - HASHC; - /* FALLTHROUGH */ - case 7: - HASHC; - /* FALLTHROUGH */ - case 6: - HASHC; - /* FALLTHROUGH */ - case 5: - HASHC; - /* FALLTHROUGH */ - case 4: - HASHC; - /* FALLTHROUGH */ - case 3: - HASHC; - /* FALLTHROUGH */ - case 2: - HASHC; - /* FALLTHROUGH */ - case 1: - HASHC; - } - while (--loop); - } + switch ((len & (4 - 1))) + { + case 0: + /* h starts out as zero so no need to include the multiply. */ + h = *key++; + /* FALLTHROUGH */ + case 3: + HASHC; + /* FALLTHROUGH */ + case 2: + HASHC; + /* FALLTHROUGH */ + case 1: + HASHC; + /* FALLTHROUGH */ + } + + uint32_t c0, c1, c2, c3; + for (--len; len >= 4; len -= 4) + { + c0 = (unsigned char) *(key + 0); + c1 = (unsigned char) *(key + 1); + c2 = (unsigned char) *(key + 2); + c3 = (unsigned char) *(key + 3); + h = HASH_CONST_P4 * h + HASH_CONST_P3 * c0 + HASH_CONST_P2 * c1 + + HASH_CONST_P1 * c2 + HASH_CONST_P0 * c3; + + key += 4; + } } return h; }