From mboxrd@z Thu Jan 1 00:00:00 1970 From: tip-bot for Mikulas Patocka Subject: [tip:x86/asm] x86/asm: Optimize memcpy_flushcache() Date: Mon, 10 Sep 2018 23:22:19 -0700 Message-ID: References: Reply-To: peterz@infradead.org, hpa@zytor.com, tglx@linutronix.de, mpatocka@redhat.com, snitzer@redhat.com, mingo@kernel.org, dm-devel@redhat.com, linux-kernel@vger.kernel.org, dan.j.williams@intel.com, torvalds@linux-foundation.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: linux-tip-commits@vger.kernel.org Cc: mingo@kernel.org, hpa@zytor.com, peterz@infradead.org, tglx@linutronix.de, mpatocka@redhat.com, snitzer@redhat.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, dan.j.williams@intel.com, dm-devel@redhat.com List-Id: dm-devel.ids Commit-ID: 02101c45ec5b19d607af7372680f5259050b4e9c Gitweb: https://git.kernel.org/tip/02101c45ec5b19d607af7372680f5259050b4e9c Author: Mikulas Patocka AuthorDate: Wed, 8 Aug 2018 17:22:16 -0400 Committer: Ingo Molnar CommitDate: Mon, 10 Sep 2018 15:17:12 +0200 x86/asm: Optimize memcpy_flushcache() I use memcpy_flushcache() in my persistent memory driver for metadata updates, there are many 8-byte and 16-byte updates and it turns out that the overhead of memcpy_flushcache causes 2% performance degradation compared to "movnti" instruction explicitly coded using inline assembler. The tests were done on a Skylake processor with persistent memory emulated using the "memmap" kernel parameter. dd was used to copy data to the dm-writecache target. This patch recognizes memcpy_flushcache calls with constant short length and turns them into inline assembler - so that I don't have to use inline assembler in the driver. Signed-off-by: Mikulas Patocka Cc: Dan Williams Cc: Linus Torvalds Cc: Mike Snitzer Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: device-mapper development Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1808081720460.24747@file01.intranet.prod.int.rdu2.redhat.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/string_64.h | 20 +++++++++++++++++++- arch/x86/lib/usercopy_64.c | 4 ++-- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index d33f92b9fa22..7ad41bfcc16c 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -149,7 +149,25 @@ memcpy_mcsafe(void *dst, const void *src, size_t cnt) #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE #define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1 -void memcpy_flushcache(void *dst, const void *src, size_t cnt); +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); +} #endif #endif /* __KERNEL__ */ diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c index 9c5606d88f61..c50a1d815a37 100644 --- a/arch/x86/lib/usercopy_64.c +++ b/arch/x86/lib/usercopy_64.c @@ -153,7 +153,7 @@ long __copy_user_flushcache(void *dst, const void __user *src, unsigned size) return rc; } -void memcpy_flushcache(void *_dst, const void *_src, size_t size) +void __memcpy_flushcache(void *_dst, const void *_src, size_t size) { unsigned long dest = (unsigned long) _dst; unsigned long source = (unsigned long) _src; @@ -216,7 +216,7 @@ void memcpy_flushcache(void *_dst, const void *_src, size_t size) clean_cache_range((void *) dest, size); } } -EXPORT_SYMBOL_GPL(memcpy_flushcache); +EXPORT_SYMBOL_GPL(__memcpy_flushcache); void memcpy_page_flushcache(char *to, struct page *page, size_t offset, size_t len)