[dpdk-dev] [PATCH v8 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>
---

  v8 Changes:
   - add SPDX license tags.

  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                               | 2 +-
 lib/librte_sched/Makefile                                        | 2 --
 lib/librte_sched/rte_sched.c                                     | 2 +-
 8 files changed, 5 insertions(+), 4 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 c6940760f..028e81dd8 100644
--- a/lib/librte_eal/bsdapp/eal/Makefile
+++ b/lib/librte_eal/bsdapp/eal/Makefile
@@ -57,6 +57,7 @@ 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 96904dea1..ea824a3a8 100644
--- a/lib/librte_eal/common/Makefile
+++ b/lib/librte_eal/common/Makefile
@@ -16,6 +16,7 @@ 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 rte_hypervisor.h rte_test.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 7bf278f3b..e50b73a69 100644
--- a/lib/librte_eal/linuxapp/eal/Makefile
+++ b/lib/librte_eal/linuxapp/eal/Makefile
@@ -64,6 +64,7 @@ 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 7088b7230..730966407 100644
--- a/lib/librte_eal/rte_eal_version.map
+++ b/lib/librte_eal/rte_eal_version.map
@@ -206,7 +206,7 @@ DPDK_18.02 {
 	rte_hypervisor_get;
 	rte_hypervisor_get_name;
 	rte_vfio_clear_group;
-
+	rte_reciprocal_value;
 } DPDK_17.11;

 EXPERIMENTAL {
diff --git a/lib/librte_sched/Makefile b/lib/librte_sched/Makefile
index 73c9d1a37..55d9c6989 100644
--- a/lib/librte_sched/Makefile
+++ b/lib/librte_sched/Makefile
@@ -26,10 +26,8 @@ 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 ad2f7c6d5..634486c80 100644
--- a/lib/librte_sched/rte_sched.c
+++ b/lib/librte_sched/rte_sched.c
@@ -14,11 +14,11 @@
 #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