===================================================================
@@ -147,7 +147,25 @@ memcpy_mcsafe(void *dst, const void *src
#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__ */
===================================================================
@@ -133,7 +133,7 @@ long __copy_user_flushcache(void *dst, c
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
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)
I use memcpy_flushcache in my persistent memory driver for metadata updates and it turns out that the overhead of memcpy_flushcache causes 2% performance degradation compared to "movnti" instruction explicitly coded using inline assembler. 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 <mpatocka@redhat.com> --- arch/x86/include/asm/string_64.h | 20 +++++++++++++++++++- arch/x86/lib/usercopy_64.c | 4 ++-- 2 files changed, 21 insertions(+), 3 deletions(-) -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel