From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sun, 25 Sep 2016 16:31:11 +0000 (-0400)
Subject: Performance: implement lttng_inline_memcpy
X-Git-Tag: v2.9.0-rc1~9
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=51b8f2fa2b972e62117caa946dd3e3565b6ca4a3;p=lttng-ust.git

Performance: implement lttng_inline_memcpy

Because all length parameters received for serializing data coming from
applications go through a callback, they are never constant, and it
hurts performance to perform a call to memcpy each time.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/libringbuffer/backend_internal.h b/libringbuffer/backend_internal.h
index 90088b89..e597cf4d 100644
--- a/libringbuffer/backend_internal.h
+++ b/libringbuffer/backend_internal.h
@@ -592,6 +592,28 @@ int update_read_sb_index(const struct lttng_ust_lib_ring_buffer_config *config,
 #define inline_memcpy(dest, src, n)	memcpy(dest, src, n)
 #endif
 
+static inline __attribute__((always_inline))
+void lttng_inline_memcpy(void *dest, const void *src,
+		unsigned long len)
+{
+	switch (len) {
+	case 1:
+		*(uint8_t *) dest = *(const uint8_t *) src;
+		break;
+	case 2:
+		*(uint16_t *) dest = *(const uint16_t *) src;
+		break;
+	case 4:
+		*(uint32_t *) dest = *(const uint32_t *) src;
+		break;
+	case 8:
+		*(uint64_t *) dest = *(const uint64_t *) src;
+		break;
+	default:
+		inline_memcpy(dest, src, len);
+	}
+}
+
 /*
  * Use the architecture-specific memcpy implementation for constant-sized
  * inputs, but rely on an inline memcpy for length statically unknown.
@@ -603,7 +625,7 @@ do {								\
 	if (__builtin_constant_p(len))				\
 		memcpy(dest, src, __len);			\
 	else							\
-		inline_memcpy(dest, src, __len);		\
+		lttng_inline_memcpy(dest, src, __len);		\
 } while (0)
 
 /*