From 934274065a596f7fc7d4d5bfe5ab039390915a49 Mon Sep 17 00:00:00 2001
From: Marvin Liu <yong.liu@intel.com>
Date: Fri, 25 Oct 2019 00:08:22 +0800
Subject: [PATCH] vhost: try to unroll for each loop

Create macro for adding unroll pragma before for each loop. Batch
functions will be contained of several small loops which can be
optimized by compilers' loop unrolling pragma.

Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/Makefile    | 18 ++++++++++++++++++
 lib/librte_vhost/meson.build |  7 +++++++
 lib/librte_vhost/vhost.h     | 24 ++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/lib/librte_vhost/Makefile b/lib/librte_vhost/Makefile
index 8623e91c0f..87ce1fb270 100644
--- a/lib/librte_vhost/Makefile
+++ b/lib/librte_vhost/Makefile
@@ -16,6 +16,24 @@ CFLAGS += -I vhost_user
 CFLAGS += -fno-strict-aliasing
 LDLIBS += -lpthread
 
+ifeq ($(RTE_TOOLCHAIN), gcc)
+ifeq ($(shell test $(GCC_VERSION) -ge 83 && echo 1), 1)
+CFLAGS += -DVHOST_GCC_UNROLL_PRAGMA
+endif
+endif
+
+ifeq ($(RTE_TOOLCHAIN), clang)
+ifeq ($(shell test $(CLANG_MAJOR_VERSION)$(CLANG_MINOR_VERSION) -ge 37 && echo 1), 1)
+CFLAGS += -DVHOST_CLANG_UNROLL_PRAGMA
+endif
+endif
+
+ifeq ($(RTE_TOOLCHAIN), icc)
+ifeq ($(shell test $(ICC_MAJOR_VERSION) -ge 16 && echo 1), 1)
+CFLAGS += -DVHOST_ICC_UNROLL_PRAGMA
+endif
+endif
+
 ifeq ($(CONFIG_RTE_LIBRTE_VHOST_NUMA),y)
 LDLIBS += -lnuma
 endif
diff --git a/lib/librte_vhost/meson.build b/lib/librte_vhost/meson.build
index cb1123ae35..00435777e2 100644
--- a/lib/librte_vhost/meson.build
+++ b/lib/librte_vhost/meson.build
@@ -8,6 +8,13 @@ endif
 if has_libnuma == 1
 	dpdk_conf.set10('RTE_LIBRTE_VHOST_NUMA', true)
 endif
+if (toolchain == 'gcc' and cc.version().version_compare('>=8.3.0'))
+	cflags += '-DVHOST_GCC_UNROLL_PRAGMA'
+elif (toolchain == 'clang' and cc.version().version_compare('>=3.7.0'))
+	cflags += '-DVHOST_CLANG_UNROLL_PRAGMA'
+elif (toolchain == 'icc' and cc.version().version_compare('>=16.0.0'))
+	cflags += '-DVHOST_ICC_UNROLL_PRAGMA'
+endif
 dpdk_conf.set('RTE_LIBRTE_VHOST_POSTCOPY',
 	      cc.has_header('linux/userfaultfd.h'))
 version = 4
diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 02b3c91fff..a2b9221e0d 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -39,6 +39,30 @@
 
 #define VHOST_LOG_CACHE_NR 32
 
+#define PACKED_BATCH_SIZE (RTE_CACHE_LINE_SIZE / \
+			    sizeof(struct vring_packed_desc))
+#define PACKED_BATCH_MASK (PACKED_BATCH_SIZE - 1)
+
+#ifdef VHOST_GCC_UNROLL_PRAGMA
+#define vhost_for_each_try_unroll(iter, val, size) _Pragma("GCC unroll 4") \
+	for (iter = val; iter < size; iter++)
+#endif
+
+#ifdef VHOST_CLANG_UNROLL_PRAGMA
+#define vhost_for_each_try_unroll(iter, val, size) _Pragma("unroll 4") \
+	for (iter = val; iter < size; iter++)
+#endif
+
+#ifdef VHOST_ICC_UNROLL_PRAGMA
+#define vhost_for_each_try_unroll(iter, val, size) _Pragma("unroll (4)") \
+	for (iter = val; iter < size; iter++)
+#endif
+
+#ifndef vhost_for_each_try_unroll
+#define vhost_for_each_try_unroll(iter, val, num) \
+	for (iter = val; iter < num; iter++)
+#endif
+
 /**
  * Structure contains buffer address, length and descriptor index
  * from vring to do scatter RX.
-- 
2.20.1