[dpdk-dev] [PATCH v7 1/3] eal: introduce integer divide through reciprocal

[Pavan Nikhilesh]

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 at caviumnetworks.com>
---

v7 changes:
 - reworked u64 division (follows same flow as 32bit).
 - addressed review comments from v6 (Undo cosmetic changes to 32bit division)

v6 changes:
 - remove cache alignment from rte_reciprocal_u{32/64}structures as they would
 be embedded in other structures.

v5 changes:
 - fix test print strings

v4 changes:
 - minor fix for test cases
 - fix u32 divisor generation

v3 changes:
 - fix x86_32 compilation issue
 - fix improper licence in test

v2 changes:
 - fix compilation issues with .map files
 - add test cases for correctness and performance
 - remove extra licence inclusion
 - fix coding style issues

 lib/librte_eal/bsdapp/eal/Makefile                               | 1 +
 lib/librte_eal/common/Makefile                                   | 1 +
 lib/{librte_sched => librte_eal/common/include}/rte_reciprocal.h | 0
 lib/{librte_sched => librte_eal/common}/rte_reciprocal.c         | 0
 lib/librte_eal/linuxapp/eal/Makefile                             | 1 +
 lib/librte_eal/rte_eal_version.map                               | 7 +++++++
 lib/librte_sched/Makefile                                        | 2 --
 lib/librte_sched/rte_sched.c                                     | 2 +-
 8 files changed, 11 insertions(+), 3 deletions(-)
 rename lib/{librte_sched => librte_eal/common/include}/rte_reciprocal.h (100%)
 rename lib/{librte_sched => librte_eal/common}/rte_reciprocal.c (100%)

diff --git a/lib/librte_eal/bsdapp/eal/Makefile b/lib/librte_eal/bsdapp/eal/Makefile
index afa117de4..b0442a75d 100644
--- a/lib/librte_eal/bsdapp/eal/Makefile
+++ b/lib/librte_eal/bsdapp/eal/Makefile
@@ -84,6 +84,7 @@ 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/common/Makefile b/lib/librte_eal/common/Makefile
index 9effd0d45..ed0d3f80b 100644
--- a/lib/librte_eal/common/Makefile
+++ b/lib/librte_eal/common/Makefile
@@ -44,6 +44,7 @@ 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_bitmap.h rte_vfio.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 100%
rename from lib/librte_sched/rte_reciprocal.h
rename to lib/librte_eal/common/include/rte_reciprocal.h
diff --git a/lib/librte_sched/rte_reciprocal.c b/lib/librte_eal/common/rte_reciprocal.c
similarity index 100%
rename from lib/librte_sched/rte_reciprocal.c
rename to lib/librte_eal/common/rte_reciprocal.c
diff --git a/lib/librte_eal/linuxapp/eal/Makefile b/lib/librte_eal/linuxapp/eal/Makefile
index 5a7b8b2ac..ce65d5ccc 100644
--- a/lib/librte_eal/linuxapp/eal/Makefile
+++ b/lib/librte_eal/linuxapp/eal/Makefile
@@ -91,6 +91,7 @@ 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/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
index f4f46c1be..d8b968c5c 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -200,6 +200,13 @@ DPDK_17.11 {

 } DPDK_17.08;

+DPDK_18.02 {
+	global:
+
+	rte_reciprocal_value;
+
+}  DPDK_17.11;
+
 EXPERIMENTAL {
 	global:

diff --git a/lib/librte_sched/Makefile b/lib/librte_sched/Makefile
index 04785f720..535b23d76 100644
--- a/lib/librte_sched/Makefile
+++ b/lib/librte_sched/Makefile
@@ -54,10 +54,8 @@ 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-$(CONFIG_RTE_LIBRTE_SCHED)-include := rte_sched.h rte_sched_common.h rte_red.h rte_approx.h
-SYMLINK-$(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 7252f850d..35c5c3cde 100644
--- a/lib/librte_sched/rte_sched.c
+++ b/lib/librte_sched/rte_sched.c
@@ -43,11 +43,11 @@
 #include <rte_branch_prediction.h>
 #include <rte_mbuf.h>
 #include <rte_bitmap.h>
+#include <rte_reciprocal.h>

 #include "rte_sched.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 */
--
2.14.1