> On Thu, Oct 08, 2020 at 01:07:26PM +0000, Ananyev, Konstantin 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; > > > +} > > > + > > > +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, > > > > While I do understand the idea of having that value from consistency point > > of view, > > I wonder do we really need to allow user to specify values smaller then 128. > > At least on x86 we always have 128 bit SIMD enabled, even for > > -Dmachine=default. > > So seems no much point to forbid libraries using SSE code-path when compiler > > is free to insert SSE instructions on its own will. > > > > The reason to support this is for testing purposes, as it allows an easy > way for a tester to check out any scalar code paths - which are often > common across architectures.
If it is just for testing things in a consistent way, then it is probably ok. The thing that worries me - later in this series there are patches that insert extra checks into inline functions that use SSE instincts: https://patches.dpdk.org/patch/79355/ (lpm: choose vector path at runtime). Which seems like a total overkill for me. > > > > + RTE_MAX_128_SIMD = 128, > > > + RTE_MAX_256_SIMD = 256, > > > + RTE_MAX_512_SIMD = 512, > > > + RTE_MAX_SIMD_DISABLE = UINT16_MAX, > > > > As a nit, I think it is safe enough to have this last value > > (RTE_MAX_SIMD_DISABLE or RTE_MAX_SIMD_MAX) equal to (INT16_MAX + 1). > > That would be big enough to probably never hit actual HW limit, > > while it still remains power of two, as other values. > > > > I actually think it's probably clearer as-is, because the fact of the rest > being powers of 2 is irrelevant since we just check greater than or less > than. Well, rte_set_max_simd_bitwidth() does accept only power of two values _AND_ this special one (UINT16_MAX). By changing it to 2^15, we can remove that special value test. > If we did change it, then we need to put in a comment explaining why > the plus-one, I don't think it is that big deal to put a comment, plus for UINT16_MAX we do need some explanation too, right? >while as it is now it's clearly a placeholder $BIGNUM. > > /Bruce