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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 844F1C43603 for ; Mon, 16 Dec 2019 21:42:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F7C324673 for ; Mon, 16 Dec 2019 21:42:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727480AbfLPVm5 (ORCPT ); Mon, 16 Dec 2019 16:42:57 -0500 Received: from mga06.intel.com ([134.134.136.31]:3598 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726275AbfLPVm5 (ORCPT ); Mon, 16 Dec 2019 16:42:57 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Dec 2019 13:42:55 -0800 X-IronPort-AV: E=Sophos;i="5.69,323,1571727600"; d="scan'208,223";a="209457143" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Dec 2019 13:42:55 -0800 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] x86/cpufeatures: Add support for fast short rep mov Date: Mon, 16 Dec 2019 13:42:54 -0800 Message-Id: <20191216214254.26492-1-tony.luck@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191212225210.GA22094@zn.tnic> References: <20191212225210.GA22094@zn.tnic> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >From the Intel Optimization Reference Manual: 3.7.6.1 Fast Short REP MOVSB Beginning with processors based on Ice Lake Client microarchitecture, REP MOVSB performance of short operations is enhanced. The enhancement applies to string lengths between 1 and 128 bytes long. Support for fast-short REP MOVSB is enumerated by the CPUID feature flag: CPUID [EAX=7H, ECX=0H).EDX.FAST_SHORT_REP_MOVSB[bit 4] = 1. There is no change in the REP STOS performance. Add an X86_FEATURE_FSRM flag for this. memmove() avoids REP MOVSB for short (< 32 byte) copies. Fix it to check FSRM and use REP MOVSB for short copies on systems that support it. Signed-off-by: Tony Luck --- Time (cycles) for memmove() sizes 1..31 with neither source nor destination in cache. 1800 +-+-------+--------+---------+---------+---------+--------+-------+-+ + + + + + + + + 1600 +-+ 'memmove-fsrm' *******-+ | ###### 'memmove-orig' ####### | 1400 +-+ # ##################### +-+ | # ############ | 1200 +-+# ################## +-+ | # | 1000 +-+# +-+ | # | | # | 800 +-# +-+ | # | 600 +-*********************** +-+ | ***************************** | 400 +-+ ******* +-+ | | 200 +-+ +-+ + + + + + + + + 0 +-+-------+--------+---------+---------+---------+--------+-------+-+ 0 5 10 15 20 25 30 35 --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/lib/memmove_64.S | 6 +++--- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index e9b62498fe75..98c60fa31ced 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -357,6 +357,7 @@ /* Intel-defined CPU features, CPUID level 0x00000007:0 (EDX), word 18 */ #define X86_FEATURE_AVX512_4VNNIW (18*32+ 2) /* AVX-512 Neural Network Instructions */ #define X86_FEATURE_AVX512_4FMAPS (18*32+ 3) /* AVX-512 Multiply Accumulation Single precision */ +#define X86_FEATURE_FSRM (18*32+ 4) /* Fast Short Rep Mov */ #define X86_FEATURE_AVX512_VP2INTERSECT (18*32+ 8) /* AVX-512 Intersect for D/Q */ #define X86_FEATURE_MD_CLEAR (18*32+10) /* VERW clears CPU buffers */ #define X86_FEATURE_TSX_FORCE_ABORT (18*32+13) /* "" TSX_FORCE_ABORT */ diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S index 337830d7a59c..4a23086806e6 100644 --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -29,10 +29,7 @@ SYM_FUNC_START_ALIAS(memmove) SYM_FUNC_START(__memmove) - /* Handle more 32 bytes in loop */ mov %rdi, %rax - cmp $0x20, %rdx - jb 1f /* Decide forward/backward copy mode */ cmp %rdi, %rsi @@ -43,6 +40,7 @@ SYM_FUNC_START(__memmove) jg 2f .Lmemmove_begin_forward: + ALTERNATIVE "cmp $0x20, %rdx; jb 1f", "", X86_FEATURE_FSRM ALTERNATIVE "", "movq %rdx, %rcx; rep movsb; retq", X86_FEATURE_ERMS /* @@ -114,6 +112,8 @@ SYM_FUNC_START(__memmove) */ .p2align 4 2: + cmp $0x20, %rdx + jb 1f cmp $680, %rdx jb 6f cmp %dil, %sil -- 2.20.1