From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45441C433EF for ; Wed, 17 Nov 2021 21:02:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22AB261B43 for ; Wed, 17 Nov 2021 21:02:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240088AbhKQVF5 (ORCPT ); Wed, 17 Nov 2021 16:05:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231750AbhKQVFx (ORCPT ); Wed, 17 Nov 2021 16:05:53 -0500 Received: from mail-io1-xd30.google.com (mail-io1-xd30.google.com [IPv6:2607:f8b0:4864:20::d30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4779C061570 for ; Wed, 17 Nov 2021 13:02:54 -0800 (PST) Received: by mail-io1-xd30.google.com with SMTP id y16so5072414ioc.8 for ; Wed, 17 Nov 2021 13:02:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=p79Xp/FScKBOK1DdTtLvla9LFFi0dfV8yzNPcgUoSpM=; b=j6L7E/2VhafB3YXISK9ewKC/k9fDgMmotC9DnNaIsabuf5oNYRY2ZY74tsDOG8O/xV WqXLeKKwtApPTYcuXDG+sBngFLTWRAOjn2v4ejgsPCf+VmUf8jlgrSwEJe6N4zn0Dcdr zE8D6GBcXGlv/T3wzdGeVv8ZeuvbIcrexi0UMc5YPpt4ntOCke6Z62fvfbgCmXOg8LLo UD+uZbQMIOoUVVXkSKNv/pB11cMaiZeyAsxm7ShFwJYjJQvzApdqcot+Y4HtKHWuF42R K5G+9AYVsooj41o6fe5UvPNRQrrv4+nrg/dU308YJvjVJLQVZz2n4yZY0EoQz6vgt6/w hoxQ== 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=p79Xp/FScKBOK1DdTtLvla9LFFi0dfV8yzNPcgUoSpM=; b=Yx3Qsp2fOoQcMmIHlKHUZqTolkPbIdVgf2vOBNBoPXrZ+pBX5TfT2GFY+ClmSl1YWy Yi6joMskLOiu3EAErExXFnj8SciZ9d5uDaLw64xEBZC44ILyeKKkXa5pgjZHp4dh+QZx BH39btnQxIy2ucPZoOTh8UH+sKPnt58NIopQZOrTdmZkBve5x39aG6iwH2pIEsqIBd4x A2GmnbjYwOrkkEG+c4SKqFG/KGmNjqYTC6m6ZX322mNx2IcJYnLqs5MhR9KcA2Wt2MMK 0swljOv3h6xaFoGYKkk4NHN9tDUqcZaQjU4crPjSiy4q2HZvjStI33ZQypq632RtVzMo izGQ== X-Gm-Message-State: AOAM530xpImfOkwuucHAC45HKuqrBeTHV7eRDIJq5g+BagOADWpuMNzs WHqV/8AcU7MUjpTctK+D5amZletN2Tw= X-Google-Smtp-Source: ABdhPJzK+gmT9BDpz8B35ahmycSSF4ahpfZFK+xkZ39Qi9EXzfnKIHYxZY9mSBUbq9OgM0K1xGomwA== X-Received: by 2002:a6b:5c05:: with SMTP id z5mr13115639ioh.181.1637182974292; Wed, 17 Nov 2021 13:02:54 -0800 (PST) Received: from localhost.localdomain (node-17-161.flex.volo.net. [76.191.17.161]) by smtp.googlemail.com with ESMTPSA id b4sm535226iot.45.2021.11.17.13.02.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Nov 2021 13:02:54 -0800 (PST) From: Noah Goldstein Cc: goldstein.w.n@gmail.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, luto@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4] arch/x86: Improve 'rep movs{b|q}' usage in memmove_64.S Date: Wed, 17 Nov 2021 15:02:45 -0600 Message-Id: <20211117210245.843374-1-goldstein.w.n@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211101044955.2295495-1-goldstein.w.n@gmail.com> References: <20211101044955.2295495-1-goldstein.w.n@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: unlisted-recipients:; (no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add check for "short distance movsb" for forwards FSRM usage and entirely remove backwards 'rep movsq'. Both of these usages hit "slow modes" that are an order of magnitude slower than usual. 'rep movsb' has some noticeable VERY slow modes that the current implementation is either 1) not checking for or 2) intentionally using. All times are in cycles and measuring the throughput of copying 1024 bytes. 1. For FSRM, when 'dst - src' is in (1, 63] or (4GB, 4GB + 63] it is an order of magnitude slower than normal and much slower than a 4x 'movq' loop. FSRM forward (dst - src == 32) -> 1113.156 FSRM forward (dst - src == 64) -> 120.669 ERMS forward (dst - src == 32) -> 209.326 ERMS forward (dst - src == 64) -> 118.22 2. For both FSRM and ERMS backwards 'rep movsb' is always slow. Both of the times below are with dst % 256 == src % 256 which mirrors the usage of the previous implementation. FSRM backward -> 1196.039 ERMS backward -> 1191.873 As a reference this is how a 4x 'movq' performances: 4x Forward (dst - src == 32) -> 128.273 4x Backward -> 130.183 Signed-off-by: Noah Goldstein --- arch/x86/lib/memmove_64.S | 38 +++++++++++++------------------------- 1 file changed, 13 insertions(+), 25 deletions(-) diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S index 64801010d312..910b963388b1 100644 --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -28,6 +28,8 @@ SYM_FUNC_START_WEAK(memmove) SYM_FUNC_START(__memmove) mov %rdi, %rax + cmp $0x20, %rdx + jb 1f /* Decide forward/backward copy mode */ cmp %rdi, %rsi @@ -39,7 +41,17 @@ SYM_FUNC_START(__memmove) /* FSRM implies ERMS => no length checks, do the copy directly */ .Lmemmove_begin_forward: - ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM + /* + * Don't use FSRM 'rep movsb' if 'dst - src' in (0, 63] or (4GB, 4GB + + * 63]. It hits a slow case which is an order of magnitude slower. + */ + ALTERNATIVE " \ + mov %edi, %ecx; \ + sub %esi, %ecx; \ + cmp $63, %ecx; \ + jbe 3f \ + ", "", X86_FEATURE_FSRM + ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; retq", X86_FEATURE_ERMS /* @@ -89,35 +101,11 @@ SYM_FUNC_START(__memmove) jmp 13f .Lmemmove_end_forward: - /* - * Handle data backward by movsq. - */ - .p2align 4 -7: - movq %rdx, %rcx - movq (%rsi), %r11 - movq %rdi, %r10 - leaq -8(%rsi, %rdx), %rsi - leaq -8(%rdi, %rdx), %rdi - shrq $3, %rcx - std - rep movsq - cld - movq %r11, (%r10) - jmp 13f - /* * Start to prepare for backward copy. */ .p2align 4 2: - cmp $0x20, %rdx - jb 1f - cmp $680, %rdx - jb 6f - cmp %dil, %sil - je 7b -6: /* * Calculate copy position to tail. */ -- 2.25.1