>
> > When choosing a vector path to take, an extra condition must be
> > satisfied to ensure the max SIMD bitwidth allows for the CPU enabled
> > path.
> >
> > The vector path was initially chosen in RTE_INIT, however this is no
> > longer suitable as we cannot check the max SIMD bitwidth at that time.
> > Default handlers are now chosen in RTE_INIT, these default handlers
> > are used the first time the crc calc is called, and they set the suitable
> > handlers to be used going forward.
> >
> > Suggested-by: Jasvinder Singh <jasvinder.si...@intel.com>
> > Suggested-by: Olivier Matz <olivier.m...@6wind.com>
> >
> > Signed-off-by: Ciara Power <ciara.po...@intel.com>
> >
> > ---
> > v4:
> > - Added default handlers to be set at RTE_INIT time, rather than
> > choosing scalar handlers.
> > - Modified logging.
> > - Updated enum name.
> > v3:
> > - Moved choosing vector paths out of RTE_INIT.
> > - Moved checking max_simd_bitwidth into the set_alg function.
> > ---
> > lib/librte_net/rte_net_crc.c | 75 ++++++++++++++++++++++++++++++------
> > lib/librte_net/rte_net_crc.h | 8 ++++
> > 2 files changed, 72 insertions(+), 11 deletions(-)
> >
> > diff --git a/lib/librte_net/rte_net_crc.c b/lib/librte_net/rte_net_crc.c
> > index 4f5b9e8286..11d0161a32 100644
> > --- a/lib/librte_net/rte_net_crc.c
> > +++ b/lib/librte_net/rte_net_crc.c
> > @@ -9,6 +9,7 @@
> > #include <rte_cpuflags.h>
> > #include <rte_common.h>
> > #include <rte_net_crc.h>
> > +#include <rte_eal.h>
> >
> > #if defined(RTE_ARCH_X86_64) && defined(__PCLMUL__)
> > #define X86_64_SSE42_PCLMULQDQ 1
> > @@ -32,6 +33,12 @@
> > static uint32_t crc32_eth_lut[CRC_LUT_SIZE];
> > static uint32_t crc16_ccitt_lut[CRC_LUT_SIZE];
> >
> > +static uint32_t
> > +rte_crc16_ccitt_default_handler(const uint8_t *data, uint32_t data_len);
> > +
> > +static uint32_t
> > +rte_crc32_eth_default_handler(const uint8_t *data, uint32_t data_len);
> > +
> > static uint32_t
> > rte_crc16_ccitt_handler(const uint8_t *data, uint32_t data_len);
> >
> > @@ -41,7 +48,12 @@ rte_crc32_eth_handler(const uint8_t *data, uint32_t
> > data_len);
> > typedef uint32_t
> > (*rte_net_crc_handler)(const uint8_t *data, uint32_t data_len);
> >
> > -static rte_net_crc_handler *handlers;
> > +static rte_net_crc_handler handlers_default[] = {
> > + [RTE_NET_CRC16_CCITT] = rte_crc16_ccitt_default_handler,
> > + [RTE_NET_CRC32_ETH] = rte_crc32_eth_default_handler,
> > +};
> > +
> > +static rte_net_crc_handler *handlers = handlers_default;
> >
> > static rte_net_crc_handler handlers_scalar[] = {
> > [RTE_NET_CRC16_CCITT] = rte_crc16_ccitt_handler,
> > @@ -60,6 +72,9 @@ static rte_net_crc_handler handlers_neon[] = {
> > };
> > #endif
> >
> > +static uint16_t max_simd_bitwidth;
> > +RTE_LOG_REGISTER(libnet_logtype, lib.net, INFO);
> > +
> > /**
> > * Reflect the bits about the middle
> > *
> > @@ -112,6 +127,42 @@ crc32_eth_calc_lut(const uint8_t *data,
> > return crc;
> > }
> >
> > +static uint32_t
> > +rte_crc16_ccitt_default_handler(const uint8_t *data, uint32_t data_len)
> > +{
> > + if (max_simd_bitwidth == 0)
> > + max_simd_bitwidth = rte_get_max_simd_bitwidth();
> > + handlers = handlers_scalar;
> > +#ifdef X86_64_SSE42_PCLMULQDQ
> > + if (max_simd_bitwidth >= RTE_SIMD_128)
> > + handlers = handlers_sse42;
> > +#endif
> > +#ifdef ARM64_NEON_PMULL
> > + if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_PMULL) &&
> > + max_simd_bitwidth >= RTE_SIMD_128) {
> > + handlers = handlers_neon;
> > +#endif
>
> You probably don't want to make all these checks for *every* invocation
> of that function. I think it would be better:
> if (ma_simd_bitwidth == 0) {....}
> return handlers[..](...);
As another thougth - it is probably a bit safer to update max_simd_bitwidht
after handler value update.
handler = ...; rte_smp_wmb(); max_simd_width = ...;
>
> BTW, while it allows us to use best possible handler,
> such approach means extra indirect call(/jump) anyway.
> Hard to say off-hand would it affect performance,
> and if yes how significantly.
> Couldn't find any perf tests in our UT for it...
>
> > + return handlers[RTE_NET_CRC16_CCITT](data, data_len);
> > +}
> > +
> > +static uint32_t
> > +rte_crc32_eth_default_handler(const uint8_t *data, uint32_t data_len)
> > +{
> > + if (max_simd_bitwidth == 0)
> > + max_simd_bitwidth = rte_get_max_simd_bitwidth();
> > + handlers = handlers_scalar;
> > +#ifdef X86_64_SSE42_PCLMULQDQ
> > + if (max_simd_bitwidth >= RTE_SIMD_128)
> > + handlers = handlers_sse42;
> > +#endif
> > +#ifdef ARM64_NEON_PMULL
> > + if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_PMULL) &&
> > + max_simd_bitwidth >= RTE_SIMD_128) {
> > + handlers = handlers_neon;
> > +#endif
> > + return handlers[RTE_NET_CRC32_ETH](data, data_len);
> > +}
> > +
> > static void
> > rte_net_crc_scalar_init(void)
> > {
> > @@ -145,18 +196,26 @@ rte_crc32_eth_handler(const uint8_t *data, uint32_t
> > data_len)
> > void
> > rte_net_crc_set_alg(enum rte_net_crc_alg alg)
> > {
> > + if (max_simd_bitwidth == 0)
> > + max_simd_bitwidth = rte_get_max_simd_bitwidth();
> > +
> > switch (alg) {
> > #ifdef X86_64_SSE42_PCLMULQDQ
> > case RTE_NET_CRC_SSE42:
> > - handlers = handlers_sse42;
> > - break;
> > + if (max_simd_bitwidth >= RTE_SIMD_128) {
> > + handlers = handlers_sse42;
> > + return;
> > + }
> > + NET_LOG(INFO, "Max SIMD Bitwidth too low, can't use SSE\n");
> > #elif defined ARM64_NEON_PMULL
> > /* fall-through */
> > case RTE_NET_CRC_NEON:
> > - if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_PMULL)) {
> > + if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_PMULL) &&
> > + max_simd_bitwidth >= RTE_SIMD_128) {
> > handlers = handlers_neon;
> > - break;
> > + return;
> > }
> > + NET_LOG(INFO, "Max SIMD Bitwidth too low or CPU flag not
> > enabled, can't use NEON\n");
> > #endif
> > /* fall-through */
> > case RTE_NET_CRC_SCALAR:
> > @@ -184,19 +243,13 @@ rte_net_crc_calc(const void *data,
> > /* Select highest available crc algorithm as default one */
> > RTE_INIT(rte_net_crc_init)
> > {
> > - enum rte_net_crc_alg alg = RTE_NET_CRC_SCALAR;
> > -
> > rte_net_crc_scalar_init();
> >
> > #ifdef X86_64_SSE42_PCLMULQDQ
> > - alg = RTE_NET_CRC_SSE42;
> > rte_net_crc_sse42_init();
> > #elif defined ARM64_NEON_PMULL
> > if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_PMULL)) {
> > - alg = RTE_NET_CRC_NEON;
> > rte_net_crc_neon_init();
> > }
> > #endif
> > -
> > - rte_net_crc_set_alg(alg);
> > }
> > diff --git a/lib/librte_net/rte_net_crc.h b/lib/librte_net/rte_net_crc.h
> > index 16e85ca970..c942865ecf 100644
> > --- a/lib/librte_net/rte_net_crc.h
> > +++ b/lib/librte_net/rte_net_crc.h
> > @@ -7,6 +7,8 @@
> >
> > #include <stdint.h>
> >
> > +#include <rte_log.h>
> > +
> > #ifdef __cplusplus
> > extern "C" {
> > #endif
> > @@ -25,6 +27,12 @@ enum rte_net_crc_alg {
> > RTE_NET_CRC_NEON,
> > };
> >
> > +extern int libnet_logtype;
> > +
> > +#define NET_LOG(level, fmt, args...)
> > \
> > + rte_log(RTE_LOG_ ## level, libnet_logtype, "%s(): " fmt "\n", \
> > + __func__, ## args)
> > +
> > /**
> > * This API set the CRC computation algorithm (i.e. scalar version,
> > * x86 64-bit sse4.2 intrinsic version, etc.) and internal data
> > --
> > 2.22.0
