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

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

> -----Original Message-----
> From: Pavan Nikhilesh [mailto:pbhagavatula@caviumnetworks.com]
> Sent: Monday, December 4, 2017 1:22 PM
> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>;
> stephen@networkplumber.org; ktraynor@redhat.com
> Cc: dev@dpdk.org; Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH v7 1/3] eal: introduce integer divide through
> reciprocal
> 
> 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>
> ---
> 
> 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

Hi Pavan,

To make progress on this patch set, I suggest you split and resend this exact patch as a standalone patch set, so we at least move the existing 32-bit version from librte_sched to EAL for other libs/apps could use it.

Regards,
Cristian