[dpdk-dev] [PATCH v6 1/3] eal: introduce integer divide through reciprocal

Dumitrescu, Cristian cristian.dumitrescu at intel.com
Wed Sep 20 15:10:53 CEST 2017


Hi Pavan,

I think moving rte_reciprocal.[hc] to a common code area like EAL is a very good idea, so thanks for doing this work!

One ask from my side: please do not change the existing code.
1. Keep the existing name for the 32-bit API functions and data structures (no _u32 name suffix), add the _u64 suffix just for the new API functions that you add.
	- If you want, you can create aliases with _32 name suffix for the existing 32-bit API
	- The only change to rte_sched.c should be header include line: #include "rte_reciprocal.h" -> #include <rte_reciprocal.h>
2. Do not do any cosmetic changes in existing code in rte_reciprocal.[hc] (such as adding CR+LF), as they result in lots of code churn for no real value

Once these changes are done, the size of your patch set is reduced considerably.


> -----Original Message-----
> From: Pavan Nikhilesh [mailto:pbhagavatula at caviumnetworks.com]
> Sent: Wednesday, September 6, 2017 11:22 AM
> To: Dumitrescu, Cristian <cristian.dumitrescu at intel.com>;
> stephen at networkplumber.org
> Cc: dev at dpdk.org; Pavan Bhagavatula
> <pbhagavatula at caviumnetworks.com>
> Subject: [dpdk-dev] [PATCH v6 1/3] eal: introduce integer divide through
> reciprocal
> 
> From: Pavan Bhagavatula <pbhagavatula at 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 at caviumnetworks.com>
> Reviewed-by: Anatoly Burakov <anatoly.burakov at intel.com>
> ---
> 
> 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/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 aac6fd7..90d7258 100644
> --- a/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> +++ b/lib/librte_eal/bsdapp/eal/rte_eal_version.map
> @@ -237,3 +237,10 @@ EXPERIMENTAL {
>  	rte_service_unregister;
> 
>  } DPDK_17.08;
> +
> +DPDK_17.11 {
> +	global:
> +
> +	rte_reciprocal_value;
> +
> +} DPDK_17.08;
> 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);
> 

Please remove these cosmetic changes that result in code churn for no real value.

>  #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;

Please remove these cosmetic changes that result in code churn for no real value.

> 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 3a8f154..2070cba 100644
> --- a/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> +++ b/lib/librte_eal/linuxapp/eal/rte_eal_version.map
> @@ -242,3 +242,10 @@ EXPERIMENTAL {
>  	rte_service_unregister;
> 
>  } DPDK_17.08;
> +
> +DPDK_17.11 {
> +	global:
> +
> +	rte_reciprocal_value;
> +
> +} DPDK_17.08;
> 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

Regards,
Cristian



More information about the dev mailing list