[dpdk-dev] [PATCH 1/2] eal: introduce integer divide through reciprocal

[Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>]

In some use cases of integer division, denominator remains constant and
numerator varies. It is possible to optimize division for such specific
scenarios.

The librte_sched uses rte_reciprocal to optimize division so, moving it to
eal/common would allow other libraries and applications to use it.

Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
---
 lib/librte_eal/bsdapp/eal/Makefile                               | 1 +
 lib/librte_eal/bsdapp/eal/rte_eal_version.map                    | 7 +++++++
 lib/librte_eal/common/Makefile                                   | 1 +
 lib/{librte_sched => librte_eal/common/include}/rte_reciprocal.h | 6 ++++--
 lib/{librte_sched => librte_eal/common}/rte_reciprocal.c         | 6 ++++--
 lib/librte_eal/linuxapp/eal/Makefile                             | 1 +
 lib/librte_eal/linuxapp/eal/rte_eal_version.map                  | 7 +++++++
 lib/librte_sched/Makefile                                        | 2 --
 lib/librte_sched/rte_sched.c                                     | 2 +-
 9 files changed, 26 insertions(+), 7 deletions(-)
 rename lib/{librte_sched => librte_eal/common/include}/rte_reciprocal.h (87%)
 rename lib/{librte_sched => librte_eal/common}/rte_reciprocal.c (96%)

diff --git a/lib/librte_eal/bsdapp/eal/Makefile b/lib/librte_eal/bsdapp/eal/Makefile
index 005019e..56f9804 100644
--- a/lib/librte_eal/bsdapp/eal/Makefile
+++ b/lib/librte_eal/bsdapp/eal/Makefile
@@ -88,6 +88,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += malloc_elem.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += malloc_heap.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += rte_keepalive.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += rte_service.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += rte_reciprocal.c
 
 # from arch dir
 SRCS-$(CONFIG_RTE_EXEC_ENV_BSDAPP) += rte_cpuflags.c
diff --git a/lib/librte_eal/bsdapp/eal/rte_eal_version.map b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
index 79e7d31..00d5f60 100644
--- a/lib/librte_eal/bsdapp/eal/rte_eal_version.map
+++ b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
@@ -238,3 +238,10 @@ EXPERIMENTAL {
 	rte_service_unregister;
 
 } DPDK_17.08;
+
+DPDK_17.11 {
+	global:
+
+	rte_reciprocal_value;
+
+} DPDK_17.11;
diff --git a/lib/librte_eal/common/Makefile b/lib/librte_eal/common/Makefile
index e8fd67a..a680b2d 100644
--- a/lib/librte_eal/common/Makefile
+++ b/lib/librte_eal/common/Makefile
@@ -42,6 +42,7 @@ INC += rte_hexdump.h rte_devargs.h rte_bus.h rte_dev.h rte_vdev.h
 INC += rte_pci_dev_feature_defs.h rte_pci_dev_features.h
 INC += rte_malloc.h rte_keepalive.h rte_time.h
 INC += rte_service.h rte_service_component.h
+INC += rte_reciprocal.h
 
 GENERIC_INC := rte_atomic.h rte_byteorder.h rte_cycles.h rte_prefetch.h
 GENERIC_INC += rte_spinlock.h rte_memcpy.h rte_cpuflags.h rte_rwlock.h
diff --git a/lib/librte_sched/rte_reciprocal.h b/lib/librte_eal/common/include/rte_reciprocal.h
similarity index 87%
rename from lib/librte_sched/rte_reciprocal.h
rename to lib/librte_eal/common/include/rte_reciprocal.h
index 5e21f09..b6d752f 100644
--- a/lib/librte_sched/rte_reciprocal.h
+++ b/lib/librte_eal/common/include/rte_reciprocal.h
@@ -29,13 +29,15 @@ struct rte_reciprocal {
 	uint8_t sh1, sh2;
 };
 
-static inline uint32_t rte_reciprocal_divide(uint32_t a, struct rte_reciprocal R)
+static inline uint32_t
+rte_reciprocal_divide(uint32_t a, struct rte_reciprocal R)
 {
 	uint32_t t = (uint32_t)(((uint64_t)a * R.m) >> 32);
 
 	return (t + ((a - t) >> R.sh1)) >> R.sh2;
 }
 
-struct rte_reciprocal rte_reciprocal_value(uint32_t d);
+struct rte_reciprocal
+rte_reciprocal_value(uint32_t d);
 
 #endif /* _RTE_RECIPROCAL_H_ */
diff --git a/lib/librte_sched/rte_reciprocal.c b/lib/librte_eal/common/rte_reciprocal.c
similarity index 96%
rename from lib/librte_sched/rte_reciprocal.c
rename to lib/librte_eal/common/rte_reciprocal.c
index 652f023..7ab99b4 100644
--- a/lib/librte_sched/rte_reciprocal.c
+++ b/lib/librte_eal/common/rte_reciprocal.c
@@ -41,7 +41,8 @@
 /* find largest set bit.
  * portable and slow but does not matter for this usage.
  */
-static inline int fls(uint32_t x)
+static inline int
+fls(uint32_t x)
 {
 	int b;
 
@@ -53,7 +54,8 @@ static inline int fls(uint32_t x)
 	return 0;
 }
 
-struct rte_reciprocal rte_reciprocal_value(uint32_t d)
+struct rte_reciprocal
+rte_reciprocal_value(uint32_t d)
 {
 	struct rte_reciprocal R;
 	uint64_t m;
diff --git a/lib/librte_eal/linuxapp/eal/Makefile b/lib/librte_eal/linuxapp/eal/Makefile
index 90bca4d..98f3b8e 100644
--- a/lib/librte_eal/linuxapp/eal/Makefile
+++ b/lib/librte_eal/linuxapp/eal/Makefile
@@ -100,6 +100,7 @@ SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += malloc_elem.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += malloc_heap.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_keepalive.c
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_service.c
+SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_reciprocal.c
 
 # from arch dir
 SRCS-$(CONFIG_RTE_EXEC_ENV_LINUXAPP) += rte_cpuflags.c
diff --git a/lib/librte_eal/linuxapp/eal/rte_eal_version.map b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
index 468c706..ac68fb3 100644
--- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
+++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
@@ -243,3 +243,10 @@ EXPERIMENTAL {
 	rte_service_unregister;
 
 } DPDK_17.08;
+
+DPDK_17.11 {
+	global:
+
+	rte_reciprocal_value;
+
+} DPDK_17.11;
diff --git a/lib/librte_sched/Makefile b/lib/librte_sched/Makefile
index 18274e7..569656b 100644
--- a/lib/librte_sched/Makefile
+++ b/lib/librte_sched/Makefile
@@ -52,10 +52,8 @@ LIBABIVER := 1
 # all source are stored in SRCS-y
 #
 SRCS-$(CONFIG_RTE_LIBRTE_SCHED) += rte_sched.c rte_red.c rte_approx.c
-SRCS-$(CONFIG_RTE_LIBRTE_SCHED) += rte_reciprocal.c
 
 # install includes
 SYMLINK-$(CONFIG_RTE_LIBRTE_SCHED)-include := rte_sched.h rte_bitmap.h rte_sched_common.h rte_red.h rte_approx.h
-SYMLINK-$(CONFIG_RTE_LIBRTE_SCHED)-include += rte_reciprocal.h
 
 include $(RTE_SDK)/mk/rte.lib.mk
diff --git a/lib/librte_sched/rte_sched.c b/lib/librte_sched/rte_sched.c
index b7cba11..3b8ccaa 100644
--- a/lib/librte_sched/rte_sched.c
+++ b/lib/librte_sched/rte_sched.c
@@ -42,12 +42,12 @@
 #include <rte_prefetch.h>
 #include <rte_branch_prediction.h>
 #include <rte_mbuf.h>
+#include <rte_reciprocal.h>
 
 #include "rte_sched.h"
 #include "rte_bitmap.h"
 #include "rte_sched_common.h"
 #include "rte_approx.h"
-#include "rte_reciprocal.h"
 
 #ifdef __INTEL_COMPILER
 #pragma warning(disable:2259) /* conversion may lose significant bits */
-- 
2.7.4