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=-5.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 D7921C4CEC7 for ; Sat, 14 Sep 2019 10:33:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96D2E206A4 for ; Sat, 14 Sep 2019 10:33:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="f71+i13v" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729406AbfINKdv (ORCPT ); Sat, 14 Sep 2019 06:33:51 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:38644 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726313AbfINKdv (ORCPT ); Sat, 14 Sep 2019 06:33:51 -0400 Received: by mail-wm1-f68.google.com with SMTP id o184so5211927wme.3; Sat, 14 Sep 2019 03:33:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=RFGEI9cLeT+ICRrH8lD0vtyoieMj4FxXtXODF3qwM7A=; b=f71+i13vq3Vzt+nWipLQbfTuVqZubeBYWuFCwg0FexDNec5n0cV/z+qNmzQCZT/ZZW l//42cUEnqpToL1HRdkgjx2xxFn3c5WKEl7eHEtmthFI16HQFW6NB1tbY6RBeSjMR63m sgqr+jCt94Hj3NqtRpN7NnLhZkNS/21n42RVp2POepcR+LDOTI+hB/IJNi1gAV94f3Yl UMnNpYKDo6g3O/D0hmVoit10VRrlDWXvYwlqoeAqpcC7YPXw/t87ZAoQ1AWWHGwWRrk/ V4g7Beoi7Y+88r9V/BspZxxuKoT8mi4VKBd16HVhl8Xi6P5urdIF/zflhJ7f4aHa4s// WqoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=RFGEI9cLeT+ICRrH8lD0vtyoieMj4FxXtXODF3qwM7A=; b=iLuY9F/b2nvnYW8j0ShHtrcahGL0l7apFic/0nivLYRCj/kfAudpWW5XlcRY9cXAxv YOsAS9aghZSiK34ifEr2ac+hH2enSdSEVnBtSNqUzSoGDHQRDiay+b/JEdichlJSblDz LQ3b3VOpwLncNLgGHCuwxSu1lksrFhKsajSCbop4wljWGoL9Lw37sna4B0gXs21M0eDX 9OFnNy3DupjF4uFcrhQWGZmfi/ezV1mj++55Ab96I1dLJSQWJXXpV7EWLiX0SWcEVMk+ KqbPhFP3r57QxDcEgYRdBjqbBGZNxWW1vyxfY5187jrY68M7uKphOBhbDJxdyjG6ekax HSKg== X-Gm-Message-State: APjAAAWwB5Urgr7y1DXWoF5/gVv2Djhy4XWlS3ETTgUA4vfm1a+c14Zq ZGILs6ISi4TosUPw3IVIXg== X-Google-Smtp-Source: APXvYqyf09lLao/95ViAGryJPvxC4ygKdWgLm0Id9auPHTlEQq6G5zpbb1qCbwJ+u12iwzrT7ja4Ww== X-Received: by 2002:a05:600c:2308:: with SMTP id 8mr7223418wmo.67.1568457228424; Sat, 14 Sep 2019 03:33:48 -0700 (PDT) Received: from avx2 ([46.53.250.254]) by smtp.gmail.com with ESMTPSA id d9sm52720356wrc.44.2019.09.14.03.33.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 14 Sep 2019 03:33:47 -0700 (PDT) Date: Sat, 14 Sep 2019 13:33:45 +0300 From: Alexey Dobriyan To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com Cc: linux-kernel@vger.kernel.org, x86@vger.kernel.org, linux@rasmusvillemoes.dk, torvalds@linux-foundation.org Subject: [PATCH] x86_64: new and improved memset() Message-ID: <20190914103345.GA5856@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Current memset() implementation does silly things: * multiplication to get register-wide constant: waste of cycles if filler is known at compile time, * REP STOSQ followed by REP STOSB: REP STOSB setup overhead is very high because trailing length is very low (< 8) * suboptimal calling convention: REP STOSB/STOSQ favours (rdi, rcx), ABI gives (rdi, rsi, rdx). While shuffling registers is free, rcx and rdx are equivalent code generation wise. * memset_orig(): memset(..., 0, ...) could be done within 3 registers, memset(..., != 0, ...) -- within 4 registers, anything else is a waste. CPUs which required unrolling are hopefully gone by now. New implementation is based on the following observations: * c == 0 is the most common form, filler can be done with "xor eax, eax" and pushed into memset() saving 2 bytes per call and multiplication * "len" divisible by 8 is the most common form: all it takes is one pointer or unsigned long inside structure, dispatch at compile time to code without those ugly "lets fill at most 7 bytes" tails, * multiplication to get wider filler value can be done at compile time for "c != 0" with 1 insn/10 bytes at most saving multiplication. Note: "memset0" name is chosen because "bzero" is officially deprecated. Note: memset(,0,) form is interleaved into memset(,c,) form to save space. TODO: CONFIG_FORTIFY_SOURCE is enabled by distros inline "xor eax, eax; rep stosb" benchmarks testing Signed-off-by: Alexey Dobriyan --- arch/x86/boot/compressed/Makefile | 1 arch/x86/include/asm/string_64.h | 104 ++++++++++++++++++++++++++++++++++ arch/x86/lib/Makefile | 1 arch/x86/lib/memset0_64.S | 86 ++++++++++++++++++++++++++++ drivers/firmware/efi/libstub/Makefile | 2 5 files changed, 193 insertions(+), 1 deletion(-) --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -38,6 +38,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += -Wno-pointer-sign +KBUILD_CFLAGS += -D_ARCH_X86_BOOT KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ GCOV_PROFILE := n --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -15,7 +15,111 @@ extern void *memcpy(void *to, const void *from, size_t len); extern void *__memcpy(void *to, const void *from, size_t len); #define __HAVE_ARCH_MEMSET +#if defined(_ARCH_X86_BOOT) || defined(CONFIG_FORTIFY_SOURCE) void *memset(void *s, int c, size_t n); +#else +#include +#include + +/* Internal, do not use. */ +static __always_inline void memset0(void *s, size_t n) +{ + /* Internal, do not use. */ + void _memset0_mov(void); + void _memset0_rep_stosq(void); + void memset0_mov(void); + void memset0_rep_stosq(void); + void memset0_rep_stosb(void); + + if (__builtin_constant_p(n) && n == 0) { + } else if (__builtin_constant_p(n) && n == 1) { + *(uint8_t *)s = 0; + } else if (__builtin_constant_p(n) && n == 2) { + *(uint16_t *)s = 0; + } else if (__builtin_constant_p(n) && n == 4) { + *(uint32_t *)s = 0; + } else if (__builtin_constant_p(n) && n == 6) { + *(uint32_t *)s = 0; + *(uint16_t *)(s + 4) = 0; + } else if (__builtin_constant_p(n) && n == 8) { + *(uint64_t *)s = 0; + } else if (__builtin_constant_p(n) && (n & 7) == 0) { + alternative_call_2( + _memset0_mov, + _memset0_rep_stosq, X86_FEATURE_REP_GOOD, + memset0_rep_stosb, X86_FEATURE_ERMS, + ASM_OUTPUT2("=D" (s), "=c" (n)), + "D" (s), "c" (n) + : "rax", "cc", "memory" + ); + } else { + alternative_call_2( + memset0_mov, + memset0_rep_stosq, X86_FEATURE_REP_GOOD, + memset0_rep_stosb, X86_FEATURE_ERMS, + ASM_OUTPUT2("=D" (s), "=c" (n)), + "D" (s), "c" (n) + : "rax", "rsi", "cc", "memory" + ); + } +} + +/* Internal, do not use. */ +static __always_inline void memsetx(void *s, int c, size_t n) +{ + /* Internal, do not use. */ + void _memsetx_mov(void); + void _memsetx_rep_stosq(void); + void memsetx_mov(void); + void memsetx_rep_stosq(void); + void memsetx_rep_stosb(void); + + const uint64_t ccc = (uint8_t)c * 0x0101010101010101ULL; + + if (__builtin_constant_p(n) && n == 0) { + } else if (__builtin_constant_p(n) && n == 1) { + *(uint8_t *)s = ccc; + } else if (__builtin_constant_p(n) && n == 2) { + *(uint16_t *)s = ccc; + } else if (__builtin_constant_p(n) && n == 4) { + *(uint32_t *)s = ccc; + } else if (__builtin_constant_p(n) && n == 8) { + *(uint64_t *)s = ccc; + } else if (__builtin_constant_p(n) && (n & 7) == 0) { + alternative_call_2( + _memsetx_mov, + _memsetx_rep_stosq, X86_FEATURE_REP_GOOD, + memsetx_rep_stosb, X86_FEATURE_ERMS, + ASM_OUTPUT2("=D" (s), "=c" (n)), + "D" (s), "c" (n), "a" (ccc) + : "cc", "memory" + ); + } else { + alternative_call_2( + memsetx_mov, + memsetx_rep_stosq, X86_FEATURE_REP_GOOD, + memsetx_rep_stosb, X86_FEATURE_ERMS, + ASM_OUTPUT2("=D" (s), "=c" (n)), + "D" (s), "c" (n), "a" (ccc) + : "rsi", "cc", "memory" + ); + } +} + +static __always_inline void *memset(void *s, int c, size_t n) +{ + if (__builtin_constant_p(c)) { + if (c == 0) { + memset0(s, n); + } else { + memsetx(s, c, n); + } + return s; + } else { + return __builtin_memset(s, c, n); + } +} +#endif void *__memset(void *s, int c, size_t n); #define __HAVE_ARCH_MEMSET16 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -58,6 +58,7 @@ else lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o lib-y += clear_page_64.o copy_page_64.o lib-y += memmove_64.o memset_64.o + lib-y += memset0_64.o lib-y += copy_user_64.o lib-y += cmpxchg16b_emu.o endif new file mode 100644 --- /dev/null +++ b/arch/x86/lib/memset0_64.S @@ -0,0 +1,86 @@ +#include +#include + +.intel_syntax noprefix + +ENTRY(memset0_rep_stosb) + xor eax, eax +.globl memsetx_rep_stosb +memsetx_rep_stosb: + rep stosb + ret +ENDPROC(memset0_rep_stosb) +ENDPROC(memsetx_rep_stosb) +EXPORT_SYMBOL(memset0_rep_stosb) +EXPORT_SYMBOL(memsetx_rep_stosb) + +ENTRY(_memset0_rep_stosq) + xor eax, eax +.globl _memsetx_rep_stosq +_memsetx_rep_stosq: + shr rcx, 3 + rep stosq + ret +ENDPROC(_memset0_rep_stosq) +ENDPROC(_memsetx_rep_stosq) +EXPORT_SYMBOL(_memset0_rep_stosq) +EXPORT_SYMBOL(_memsetx_rep_stosq) + +ENTRY(memset0_rep_stosq) + xor eax, eax +.globl memsetx_rep_stosq +memsetx_rep_stosq: + lea rsi, [rdi + rcx] + shr rcx, 3 + rep stosq + cmp rdi, rsi + je 1f +2: + mov [rdi], al + add rdi, 1 + cmp rdi, rsi + jne 2b +1: + ret +ENDPROC(memset0_rep_stosq) +ENDPROC(memsetx_rep_stosq) +EXPORT_SYMBOL(memset0_rep_stosq) +EXPORT_SYMBOL(memsetx_rep_stosq) + +ENTRY(_memset0_mov) + xor eax, eax +.globl _memsetx_mov +_memsetx_mov: + add rcx, rdi + cmp rdi, rcx + je 1f +2: + mov [rdi], rax + add rdi, 8 + cmp rdi, rcx + jne 2b +1: + ret +ENDPROC(_memset0_mov) +ENDPROC(_memsetx_mov) +EXPORT_SYMBOL(_memset0_mov) +EXPORT_SYMBOL(_memsetx_mov) + +ENTRY(memset0_mov) + xor eax, eax +.globl memsetx_mov +memsetx_mov: + lea rsi, [rdi + rcx] + cmp rdi, rsi + je 1f +2: + mov [rdi], al + add rdi, 1 + cmp rdi, rsi + jne 2b +1: + ret +ENDPROC(memset0_mov) +ENDPROC(memsetx_mov) +EXPORT_SYMBOL(memset0_mov) +EXPORT_SYMBOL(memsetx_mov) --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -28,7 +28,7 @@ KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ -D__NO_FORTIFY \ $(call cc-option,-ffreestanding) \ $(call cc-option,-fno-stack-protector) \ - -D__DISABLE_EXPORTS + -D__DISABLE_EXPORTS -D_ARCH_X86_BOOT GCOV_PROFILE := n KASAN_SANITIZE := n