Hi Ciara,
Please find some comments below.
On Wed, Sep 30, 2020 at 02:03:57PM +0100, Ciara Power 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.po...@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)
> +{
> + 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')
> + 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;
> + 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;
> +}
Should the return value be enum rte_max_simd_t?
If not, do we really need the enum definition?
> +
> +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;
> +}
Same question, should the parameter be enum rte_max_simd_t?
> +
> 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,
> +};
What is the difference between RTE_NO_SIMD and RTE_MAX_SIMD_DISABLE?
The default value in internal_config is 0, so in my understanding
rte_get_max_simd_bitwidth() will return 0 if --force-max-simd-bitwidth
is not passed. Is it expected?
Maybe I'm missing something, but I don't understand why the value in
internal_config is not set to the maximum supported SIMD bitwidth by
default, and optionally overriden by the command line argument, or by
the API.
> +
> /**
> * 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.
> + */
> +__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
>
