From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Subject: [PATCH v2] x86: optimize memcpy_flushcache
In the context of constant short length stores to persistent memory,
memcpy_flushcache suffers from a 2% performance degradation compared to
explicitly using the "movnti" instruction.
Optimize 4, 8, and 16 byte memcpy_flushcache calls to explicitly use the
movnti instruction with inline assembler.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
arch/x86/include/asm/string_64.h | 28 +++++++++++++++++++++++++++-
arch/x86/lib/usercopy_64.c | 4 ++--
2 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index 533f74c300c2..aaba83478cdc 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -147,7 +147,33 @@ 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 volatile("movntil %1, %0"
+ : "=m" (*(u32 *)dst)
+ : "r" (*(u32 *)src));
+ return;
+ case 8:
+ asm volatile("movntiq %1, %0"
+ : "=m" (*(u64 *)dst)
+ : "r" (*(u64 *)src));
+ return;
+ case 16:
+ asm volatile("movntiq %1, %0"
+ : "=m" (*(u64 *)dst)
+ : "r" (*(u64 *)src));
+ asm volatile("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 75d3776123cc..26f515aa3529 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -133,7 +133,7 @@ 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;
@@ -196,7 +196,7 @@ 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)
--
2.15.0
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
