Re: [dpdk-dev] [PATCH v3 01/18] eal: add max SIMD bitwidth

[David Marchand <david.marchand@redhat.com>]

On Wed, Sep 30, 2020 at 3:08 PM Ciara Power <ciara.power@intel.com> wrote:
>
> This patch adds a max SIMD bitwidth EAL configuration. The API allows
> for an app to set this value. It can also be set using EAL argument
> --force-max-simd-bitwidth, which will lock the value and override any
> modifications made by the app.
>
> Signed-off-by: Ciara Power <ciara.power@intel.com>
>
> ---
> v3:
>   - Added enum value to essentially disable using max SIMD to choose
>     paths, intended for use by ARM SVE.
>   - Fixed parsing bitwidth argument to return an error for values
>     greater than uint16_t.
> v2: Added to Doxygen comment for API.
> ---
>  lib/librte_eal/common/eal_common_options.c | 64 ++++++++++++++++++++++
>  lib/librte_eal/common/eal_internal_cfg.h   |  8 +++
>  lib/librte_eal/common/eal_options.h        |  2 +
>  lib/librte_eal/include/rte_eal.h           | 33 +++++++++++
>  lib/librte_eal/rte_eal_version.map         |  4 ++
>  5 files changed, 111 insertions(+)
>
> diff --git a/lib/librte_eal/common/eal_common_options.c b/lib/librte_eal/common/eal_common_options.c
> index a5426e1234..e9117a96af 100644
> --- a/lib/librte_eal/common/eal_common_options.c
> +++ b/lib/librte_eal/common/eal_common_options.c
> @@ -102,6 +102,7 @@ eal_long_options[] = {
>         {OPT_MATCH_ALLOCATIONS, 0, NULL, OPT_MATCH_ALLOCATIONS_NUM},
>         {OPT_TELEMETRY,         0, NULL, OPT_TELEMETRY_NUM        },
>         {OPT_NO_TELEMETRY,      0, NULL, OPT_NO_TELEMETRY_NUM     },
> +       {OPT_FORCE_MAX_SIMD_BITWIDTH, 1, NULL, OPT_FORCE_MAX_SIMD_BITWIDTH_NUM},
>         {0,                     0, NULL, 0                        }
>  };
>
> @@ -1309,6 +1310,34 @@ eal_parse_iova_mode(const char *name)
>         return 0;
>  }
>
> +static int
> +eal_parse_simd_bitwidth(const char *arg, bool locked)

No need to pass a "locked" bool, we only care about forced value in
this function.


> +{
> +       char *end;
> +       unsigned long bitwidth;
> +       int ret;
> +       struct internal_config *internal_conf =
> +               eal_get_internal_configuration();
> +
> +       if (arg == NULL || arg[0] == '\0')
> +               return -1;
> +
> +       errno = 0;
> +       bitwidth = strtoul(arg, &end, 0);
> +
> +       /* check for errors */
> +       if (bitwidth > UINT16_MAX || errno != 0 || end == NULL || *end != '\0')

Nit: look at bitwidth after checking errno and consorts.


> +               return -1;
> +
> +       if (bitwidth == 0)
> +               bitwidth = UINT16_MAX;
> +       ret = rte_set_max_simd_bitwidth(bitwidth);
> +       if (ret < 0)
> +               return -1;
> +       internal_conf->max_simd_bitwidth.locked = locked;

Please align eal option and internal config field name.

--force-max-simd-bitwidth => .forced ?
And then %s/locked/forced/g


> +       return 0;
> +}
> +
>  static int
>  eal_parse_base_virtaddr(const char *arg)
>  {
> @@ -1707,6 +1736,13 @@ eal_parse_common_option(int opt, const char *optarg,
>         case OPT_NO_TELEMETRY_NUM:
>                 conf->no_telemetry = 1;
>                 break;
> +       case OPT_FORCE_MAX_SIMD_BITWIDTH_NUM:
> +               if (eal_parse_simd_bitwidth(optarg, 1) < 0) {
> +                       RTE_LOG(ERR, EAL, "invalid parameter for --"
> +                                       OPT_FORCE_MAX_SIMD_BITWIDTH "\n");
> +                       return -1;
> +               }
> +               break;
>
>         /* don't know what to do, leave this to caller */
>         default:
> @@ -1903,6 +1939,33 @@ eal_check_common_options(struct internal_config *internal_cfg)
>         return 0;
>  }
>
> +uint16_t
> +rte_get_max_simd_bitwidth(void)
> +{
> +       const struct internal_config *internal_conf =
> +               eal_get_internal_configuration();
> +       return internal_conf->max_simd_bitwidth.bitwidth;
> +}
> +
> +int
> +rte_set_max_simd_bitwidth(uint16_t bitwidth)
> +{
> +       struct internal_config *internal_conf =
> +               eal_get_internal_configuration();
> +       if (internal_conf->max_simd_bitwidth.locked) {
> +               RTE_LOG(NOTICE, EAL, "Cannot set max SIMD bitwidth - user runtime override enabled");
> +               return -EPERM;
> +       }
> +
> +       if (bitwidth != RTE_MAX_SIMD_DISABLE && (bitwidth < RTE_NO_SIMD ||
> +                       !rte_is_power_of_2(bitwidth))) {
> +               RTE_LOG(ERR, EAL, "Invalid bitwidth value!\n");
> +               return -EINVAL;
> +       }
> +       internal_conf->max_simd_bitwidth.bitwidth = bitwidth;
> +       return 0;
> +}
> +
>  void
>  eal_common_usage(void)
>  {
> @@ -1981,6 +2044,7 @@ eal_common_usage(void)
>                "  --"OPT_BASE_VIRTADDR"     Base virtual address\n"
>                "  --"OPT_TELEMETRY"   Enable telemetry support (on by default)\n"
>                "  --"OPT_NO_TELEMETRY"   Disable telemetry support\n"
> +              "  --"OPT_FORCE_MAX_SIMD_BITWIDTH" Force the max SIMD bitwidth\n"
>                "\nEAL options for DEBUG use only:\n"
>                "  --"OPT_HUGE_UNLINK"       Unlink hugepage files after init\n"
>                "  --"OPT_NO_HUGE"           Use malloc instead of hugetlbfs\n"
> diff --git a/lib/librte_eal/common/eal_internal_cfg.h b/lib/librte_eal/common/eal_internal_cfg.h
> index 13f93388a7..367e0cc19e 100644
> --- a/lib/librte_eal/common/eal_internal_cfg.h
> +++ b/lib/librte_eal/common/eal_internal_cfg.h
> @@ -33,6 +33,12 @@ struct hugepage_info {
>         int lock_descriptor;    /**< file descriptor for hugepage dir */
>  };
>
> +struct simd_bitwidth {
> +       /**< flag indicating if bitwidth is locked from further modification */
> +       bool locked;
> +       uint16_t bitwidth; /**< bitwidth value */
> +};
> +
>  /**
>   * internal configuration
>   */
> @@ -85,6 +91,8 @@ struct internal_config {
>         volatile unsigned int init_complete;
>         /**< indicates whether EAL has completed initialization */
>         unsigned int no_telemetry; /**< true to disable Telemetry */
> +       /** max simd bitwidth path to use */

/**<


> +       struct simd_bitwidth max_simd_bitwidth;
>  };
>
>  void eal_reset_internal_config(struct internal_config *internal_cfg);
> diff --git a/lib/librte_eal/common/eal_options.h b/lib/librte_eal/common/eal_options.h
> index 89769d48b4..ef33979664 100644
> --- a/lib/librte_eal/common/eal_options.h
> +++ b/lib/librte_eal/common/eal_options.h
> @@ -85,6 +85,8 @@ enum {
>         OPT_TELEMETRY_NUM,
>  #define OPT_NO_TELEMETRY      "no-telemetry"
>         OPT_NO_TELEMETRY_NUM,
> +#define OPT_FORCE_MAX_SIMD_BITWIDTH  "force-max-simd-bitwidth"
> +       OPT_FORCE_MAX_SIMD_BITWIDTH_NUM,
>         OPT_LONG_MAX_NUM
>  };
>
> diff --git a/lib/librte_eal/include/rte_eal.h b/lib/librte_eal/include/rte_eal.h
> index ddcf6a2e7a..fb739f3474 100644
> --- a/lib/librte_eal/include/rte_eal.h
> +++ b/lib/librte_eal/include/rte_eal.h
> @@ -43,6 +43,14 @@ enum rte_proc_type_t {
>         RTE_PROC_INVALID
>  };
>
> +enum rte_max_simd_t {
> +       RTE_NO_SIMD = 64,
> +       RTE_MAX_128_SIMD = 128,
> +       RTE_MAX_256_SIMD = 256,
> +       RTE_MAX_512_SIMD = 512,
> +       RTE_MAX_SIMD_DISABLE = UINT16_MAX,
> +};
> +
>  /**
>   * Get the process type in a multi-process setup
>   *
> @@ -51,6 +59,31 @@ enum rte_proc_type_t {
>   */
>  enum rte_proc_type_t rte_eal_process_type(void);
>
> +/**
> + * Get the supported SIMD bitwidth.
> + *
> + * @return
> + *   uint16_t bitwidth.
> + */
> +__rte_experimental
> +uint16_t rte_get_max_simd_bitwidth(void);
> +
> +/**
> + * Set the supported SIMD bitwidth.
> + * This API should only be called once at initialization, before EAL init.
> + *
> + * @param bitwidth
> + *   uint16_t bitwidth.
> + * @return
> + *   0 on success.
> + * @return
> + *   -EINVAL on invalid bitwidth parameter.
> + * @return
> + *   -EPERM if bitwidth is locked.

A single @return with a bullet list is preferred (note to self: fix
rte_eal_cleanup).

@return
 - 0 on success.
 - -EINVAL on invalid bitwidth parameter.
 - -EPERM if bitwidth is forced.



> + */
> +__rte_experimental
> +int rte_set_max_simd_bitwidth(uint16_t bitwidth);
> +
>  /**
>   * Request iopl privilege for all RPL.
>   *
> diff --git a/lib/librte_eal/rte_eal_version.map b/lib/librte_eal/rte_eal_version.map
> index c32461c663..17a7195a3d 100644
> --- a/lib/librte_eal/rte_eal_version.map
> +++ b/lib/librte_eal/rte_eal_version.map
> @@ -397,6 +397,10 @@ EXPERIMENTAL {
>         rte_service_lcore_may_be_active;
>         rte_thread_register;
>         rte_thread_unregister;
> +
> +       # added in 20.11
> +       rte_get_max_simd_bitwidth;
> +       rte_set_max_simd_bitwidth;
>  };
>
>  INTERNAL {
> --
> 2.17.1
>


-- 
David Marchand