From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from va-1-114.ptr.blmpb.com (va-1-114.ptr.blmpb.com [209.127.230.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF1E7405C44 for ; Wed, 3 Jun 2026 08:07:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.127.230.114 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780474067; cv=none; b=VAhGvIlauiquZEFtOgykdq+B9dig1DK0UbOIlDKabWjUUImJW2j1LAQQL8byRYa1zUNUGOqyrqw6jnkCcgMWeQdY1khOVuGSGZ5+cCyvig5S6dGbLXgoS4ly7Wibwvr80iaB80MhoNBEADlhEMUz3SAuHD++3ho1A0J04/Vsh4s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780474067; c=relaxed/simple; bh=z/Ea2k7fpYsGEUt9hh88F/a4jksvVj//QreE6FccEYs=; h=Subject:Date:From:In-Reply-To:Message-Id:Mime-Version:To: References:Content-Type:Cc; b=WLZdrW/yG+gVsO0kSrXCQWKdZ7GrUxXHDPTCdQY6acIO3HFYqxIBuib3CNLQL2uDE73akgPmRyKv+z+9H1xtcXgt4+SyIE3IlUbCBG1QOYhQi21vtS8bo8aJ+lVurjY0+Lg9vf3FNw+ZG8ph2li1Z7qM6CQMBt1ALmCvdA4Wjus= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=UzbACo83; arc=none smtp.client-ip=209.127.230.114 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="UzbACo83" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=2212171451; d=bytedance.com; t=1780474061; h=from:subject: mime-version:from:date:message-id:subject:to:cc:reply-to:content-type: mime-version:in-reply-to:message-id; bh=gRJ/J0Nb17+iEYOrMVREQ16d2zbIiv+jVQRVIwQKMg0=; b=UzbACo833+fZrHQgsSodG9/cGosdHc9uxTR0mzQTdV/YYzjBVArtNlLsAR1Fuwvu2ewzTK 6D4DJIRRTAKPLSjDCDgpzkgLVxy9k1KmkL4cqXxHo1WmZdeNhK5oAdFZF6h8Qq21bMk39d Jq9qOAMpmD9cog0JqIBZCyaVcg/6k9LU4A7Dksc5p8/Yc38fs/hQKHkpthMYuMC4praukD 8dpIf16uBEtZnyCmclYuhgprQ9MXD9HMRZv60Khhwg1M885ZWxHa54mnR+BW2Xpv1ebjte IUdRAAkeeJuY89e3CqOtB70jLu/u0qi1qrX6aCiDnhulkYt8lE/bPpaGwsQOug== Subject: [PATCH v4 7/8] x86/string: extend memcpy_flushcache() fixed-size fastpaths Date: Wed, 3 Jun 2026 16:01:51 +0800 From: "Li Zhe" In-Reply-To: <20260603080152.64728-1-lizhe.67@bytedance.com> X-Mailer: git-send-email 2.45.2 Message-Id: <20260603080152.64728-8-lizhe.67@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Original-From: Li Zhe To: , , , , , , , , , X-Lms-Return-Path: Content-Transfer-Encoding: 7bit References: <20260603080152.64728-1-lizhe.67@bytedance.com> Content-Type: text/plain; charset=UTF-8 Cc: , , , , , Small constant-sized flushcache copies currently inline only the 4, 8, and 16-byte cases. Larger constant sizes fall back to __memcpy_flushcache() even when the destination is naturally aligned. Factor the movnti sequences into 4/8/16/32/64-byte helpers and extend the inline fastpath coverage to the additional aligned constant sizes 32, 48, 64, 80, and 96 bytes. Keep the existing 4/8/16-byte cases handled directly in memcpy_flushcache() so they do not pick up the extra alignment gating used by the larger fixed-size helpers. Because memcpy_streaming() maps aligned transfers to memcpy_flushcache(), these additional fixed-size cases also stay on the inline movnti path for that helper. Issue the stores in ascending address order so write-combining sees a forward stream. Keep all other sizes on __memcpy_flushcache(), and keep zero-length copies returning immediately. Signed-off-by: Li Zhe --- arch/x86/include/asm/string_64.h | 122 ++++++++++++++++++++++++++----- 1 file changed, 104 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index aee63108577f..16d1aac2da24 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -83,24 +83,6 @@ int strcmp(const char *cs, const char *ct); #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE #define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1 void __memcpy_flushcache(void *dst, const void *src, size_t cnt); -static __always_inline void memcpy_flushcache(void *dst, const void *src, size_t cnt) -{ - if (__builtin_constant_p(cnt)) { - switch (cnt) { - case 4: - asm ("movntil %1, %0" : "=m"(*(u32 *)dst) : "r"(*(u32 *)src)); - return; - case 8: - asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src)); - return; - case 16: - asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src)); - asm ("movntiq %1, %0" : "=m"(*(u64 *)(dst + 8)) : "r"(*(u64 *)(src + 8))); - return; - } - } - __memcpy_flushcache(dst, src, cnt); -} /* * Only map memcpy_streaming() to memcpy_flushcache() when the destination @@ -115,6 +97,110 @@ static __always_inline bool memcpy_flushcache_nt_safe(const void *dst, return cnt && IS_ALIGNED(d, 8) && IS_ALIGNED(cnt, 4); } +static __always_inline void memcpy_flushcache_4(void *dst, const void *src) +{ + asm volatile("movntil %1, %0" + : "=m"(*(u32 *)dst) + : "r"(*(const u32 *)src) + : "memory"); +} + +static __always_inline void memcpy_flushcache_8(void *dst, const void *src) +{ + asm volatile("movntiq %1, %0" + : "=m"(*(u64 *)dst) + : "r"(*(const u64 *)src) + : "memory"); +} + +static __always_inline void memcpy_flushcache_16(void *dst, + const void *src) +{ + memcpy_flushcache_8(dst, src); + memcpy_flushcache_8(dst + 8, src + 8); +} + +static __always_inline void memcpy_flushcache_32(void *dst, + const void *src) +{ + memcpy_flushcache_16(dst, src); + memcpy_flushcache_16(dst + 16, src + 16); +} + +static __always_inline void memcpy_flushcache_64(void *dst, + const void *src) +{ + memcpy_flushcache_32(dst, src); + memcpy_flushcache_32(dst + 32, src + 32); +} + +/* + * Keep the additional aligned fixed-size cases on the inline movnti path. + * Leave the existing 4/8/16-byte cases handled directly in + * memcpy_flushcache() so they do not pick up the extra alignment gating + * used by the larger fixed-size helpers. + */ +static __always_inline int memcpy_flushcache_large(void *dst, + const void *src, + size_t cnt) +{ + unsigned long d = (unsigned long)dst; + char *dptr = dst; + const char *sptr = src; + + if (!IS_ALIGNED(d, 8)) + return 0; + + switch (cnt) { + case 32: + memcpy_flushcache_32(dptr, sptr); + return 1; + case 48: + memcpy_flushcache_32(dptr, sptr); + memcpy_flushcache_16(dptr + 32, sptr + 32); + return 1; + case 64: + memcpy_flushcache_64(dptr, sptr); + return 1; + case 80: + memcpy_flushcache_64(dptr, sptr); + memcpy_flushcache_16(dptr + 64, sptr + 64); + return 1; + case 96: + memcpy_flushcache_64(dptr, sptr); + memcpy_flushcache_32(dptr + 64, sptr + 64); + return 1; + } + + return 0; +} + +static __always_inline void memcpy_flushcache(void *dst, const void *src, + size_t cnt) +{ + if (!cnt) + return; + + if (__builtin_constant_p(cnt)) { + switch (cnt) { + case 4: + memcpy_flushcache_4(dst, src); + return; + case 8: + memcpy_flushcache_8(dst, src); + return; + case 16: + memcpy_flushcache_16(dst, src); + return; + } + + if (memcpy_flushcache_large(dst, src, cnt)) + return; + } + + __memcpy_flushcache(dst, src, cnt); +} + #define __HAVE_ARCH_MEMCPY_STREAMING 1 static __always_inline void memcpy_streaming(void *dst, const void *src, size_t cnt) -- 2.20.1