On 26 Sep 2022, at 15:29, Emma Finn wrote:
> This commit adds support for the AVX512 implementation of the
> ipv6_set_addrs action as well as an AVX512 implementation of
> updating the L4 checksums.
>
> Signed-off-by: Emma Finn <[email protected]>
Hi Emma,
Thanks for further enhancing the implementation of the AVX512 actions. Below
are some comments, mostly style related, but with one additional optimization.
Cheers,
Eelco
> ---
> v3:
> - Added a runtime check for AVX512 vbmi.
> v2:
> - Added check for availbility of s6_addr32 field of struct in6_addr.
> - Fixed network headers for freebsd builds.
> ---
> ---
> lib/odp-execute-avx512.c | 176 ++++++++++++++++++++++++++++++++++++++
> lib/odp-execute-private.c | 17 ++++
> lib/odp-execute-private.h | 1 +
> 3 files changed, 194 insertions(+)
>
> diff --git a/lib/odp-execute-avx512.c b/lib/odp-execute-avx512.c
> index 6c7713251..f97b3c2f7 100644
> --- a/lib/odp-execute-avx512.c
> +++ b/lib/odp-execute-avx512.c
> @@ -20,6 +20,9 @@
>
> #include <config.h>
> #include <errno.h>
> +#include <sys/types.h>
> +#include <netinet/in.h>
> +#include <netinet/ip6.h>
>
> #include "csum.h"
> #include "dp-packet.h"
> @@ -483,6 +486,172 @@ action_avx512_ipv4_set_addrs(struct dp_packet_batch
> *batch,
> }
> }
>
> +#if HAVE_AVX512VBMI
> +static inline uint16_t ALWAYS_INLINE
> +__attribute__((__target__("avx512vbmi")))
> +avx512_ipv6_get_delta(__m512i ip6_header)
I guess the function name was from before you split up this function, as it's
not at all what you're doing in this function.
I would suggest changing the name to something like avx512_ipv6_sum_header().
Also, can you go over the register naming and comment text below, as they also
make no sense in the current form?
> +{
> + __m256i v_zeros = _mm256_setzero_si256();
> + __m512i v_shuf_src_dst = _mm512_setr_epi64(0x01, 0x02, 0x03, 0x04,
> + 0xFF, 0xFF, 0xFF, 0xFF);
> +
> + __m512i v_header = _mm512_permutexvar_epi64(v_shuf_src_dst, ip6_header);
> + __m256i v_ip6_src_dst = _mm512_extracti64x4_epi64(v_header, 0);
Remove the extra space after the equal sign.
Please add a new line before the comment.
> + /* These two shuffle masks, v_swap16a and v_swap16b, are to shuffle the
> + * src and dst fields and add padding after each 16-bit value for the
> + * following carry over addition. */
> + __m256i v_swap16a = _mm256_setr_epi16(0x0100, 0xFFFF, 0x0302, 0xFFFF,
> + 0x0504, 0xFFFF, 0x0706, 0xFFFF,
> + 0x0100, 0xFFFF, 0x0302, 0xFFFF,
> + 0x0504, 0xFFFF, 0x0706, 0xFFFF);
> + __m256i v_swap16b = _mm256_setr_epi16(0x0908, 0xFFFF, 0x0B0A, 0xFFFF,
> + 0x0D0C, 0xFFFF, 0x0F0E, 0xFFFF,
> + 0x0908, 0xFFFF, 0x0B0A, 0xFFFF,
> + 0x0D0C, 0xFFFF, 0x0F0E, 0xFFFF);
> + __m256i v_shuf_old1 = _mm256_shuffle_epi8(v_ip6_src_dst, v_swap16a);
> + __m256i v_shuf_old2 = _mm256_shuffle_epi8(v_ip6_src_dst, v_swap16b);
> +
> + /* Add each part of the old and new headers together. */
> + __m256i v_delta = _mm256_add_epi32(v_shuf_old1, v_shuf_old2);
> +
> + /* Perform horizontal add to go from 8x32-bits to 2x32-bits. */
> + v_delta = _mm256_hadd_epi32(v_delta, v_zeros);
> + v_delta = _mm256_hadd_epi32(v_delta, v_zeros);
> +
> + /* Shuffle 32-bit value from 3rd lane into first lane for final
> + * horizontal add. */
> + __m256i v_swap32a = _mm256_setr_epi32(0x0, 0x4, 0xF, 0xF,
> + 0xF, 0xF, 0xF, 0xF);
> + v_delta = _mm256_permutexvar_epi32(v_swap32a, v_delta);
> +
> + v_delta = _mm256_hadd_epi32(v_delta, v_zeros);
> + v_delta = _mm256_hadd_epi16(v_delta, v_zeros);
> +
> + /* Extract delta value. */
> + return _mm256_extract_epi16(v_delta, 0);
> +}
> +
> +static inline uint16_t ALWAYS_INLINE
> +__attribute__((__target__("avx512vbmi")))
> +avx512_ipv6_addr_csum_delta(__m512i old_header, __m512i new_header)
> +{
> + uint16_t delta;
> + uint16_t old_delta = avx512_ipv6_get_delta(old_header);
> + uint16_t new_delta = avx512_ipv6_get_delta(new_header);
> + old_delta = ~old_delta;
> + uint32_t csum_delta = old_delta + new_delta;
> + delta = csum_finish(csum_delta);
> +
> + return ~delta;
This function looks rather cluttered, what about the following:
{
uint16_t old_delta = avx512_ipv6_get_delta(old_header);
uint16_t new_delta = avx512_ipv6_get_delta(new_header);
uint32_t csum_delta = ~old_delta + new_delta;
return ~csum_finish(csum_delta);
}
> +}
> +
> +/* This function performs the same operation on each packet in the batch as
> + * the scalar odp_set_ipv6() function. */
> +static void
> +__attribute__((__target__("avx512vbmi")))
> +action_avx512_ipv6_set_addrs(struct dp_packet_batch *batch,
> + const struct nlattr *a)
> +{
> + const struct ovs_key_ipv6 *key, *mask;
> + struct dp_packet *packet;
Add a new line between definitions and code.
> + a = nl_attr_get(a);
> + key = nl_attr_get(a);
> + mask = odp_get_key_mask(a, struct ovs_key_ipv6);
We have build asserts for the ovs_key_ipv4 key structure to make sure they do
not change, we should add the same for v6.
> +
> + /* Read the content of the key and mask in the respective registers. We
> + * only load the size of the actual structure, which is only 40 bytes. */
> + __m512i v_key = _mm512_maskz_loadu_epi64(0x1F, (void *) key);
> + __m512i v_mask = _mm512_maskz_loadu_epi64(0x1F, (void *) mask);
> +
> + /* This shuffle mask v_shuffle, is to shuffle key and mask to match the
> + * ip6_hdr structure layout. */
> + static const uint8_t ip_shuffle_mask[64] = {
> + 0x20, 0x21, 0x22, 0x23, 0xFF, 0xFF, 0x24, 0x26,
> + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
> + 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
> + 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
> + 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F,
> + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0XFF, 0xFF, 0xFF,
> + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
> + 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0XFF, 0xFF
> + };
> +
> + __m512i v_shuffle = _mm512_loadu_si512((void *) ip_shuffle_mask);
> +
> + /* This shuffle is required for key and mask to match the layout of the
> + * ip6_hdr struct. */
> + __m512i v_key_shuf = _mm512_permutexvar_epi8(v_shuffle, v_key);
> + __m512i v_mask_shuf = _mm512_permutexvar_epi8(v_shuffle, v_mask);
> +
> + DP_PACKET_BATCH_FOR_EACH (i, packet, batch) {
> + struct ovs_16aligned_ip6_hdr *nh = dp_packet_l3(packet);
> +
> + /* Load the 40 bytes of the IPv6 header. */
> + __m512i v_packet = _mm512_maskz_loadu_epi64(0x1F, (void *) nh);
> +
> + /* AND the v_pkt_mask to the packet data (v_packet). */
> + __m512i v_pkt_masked = _mm512_andnot_si512(v_mask_shuf, v_packet);
> +
> + /* OR the new addresses (v_key_shuf) with the masked packet addresses
> + * (v_pkt_masked). */
> + __m512i v_new_hdr = _mm512_or_si512(v_key_shuf, v_pkt_masked);
> +
> + /* If ip6_src or ip6_dst has been modified, L4 checksum needs to
> + * be updated. */
> + bool do_checksum = false;
So as we are trying to optimise code, this only needs to be done once, so we
should move this outside the DP_PACKET_BATCH_FOR_EACH() loop.
> +#ifdef s6_addr32
> + for (int j = 0; j < 4; j++) {
> + if (mask->ipv6_dst.s6_addr32[j] || mask->ipv6_src.s6_addr32[j]) {
> + do_checksum = true;
> + }
> + }
> +#else
> + for (int j = 0; j < 16; j++) {
> + if (mask->ipv6_dst.s6_addr[j] || mask->ipv6_src.s6_addr[j]) {
> + do_checksum = true;
> + }
> + }
> +#endif
Not sure how fast slow/fast the above is compared with doing an AVX512 AND on
the v_mask with a new v_address_mask + popcount?
> + if (do_checksum) {
> + uint8_t proto = nh->ip6_nxt;
> + uint16_t delta_checksum = avx512_ipv6_addr_csum_delta(v_packet,
> + v_new_hdr);
> +
> + if (proto == IPPROTO_UDP) {
> + struct udp_header *uh = dp_packet_l4(packet);
Add a new line here.
> + if (uh->udp_csum) {
> + uint16_t old_udp_checksum = ~uh->udp_csum;
> + uint32_t udp_checksum = old_udp_checksum +
> delta_checksum;
Add a new line here.
> + udp_checksum = csum_finish(udp_checksum);
> +
> + if (!udp_checksum) {
> + udp_checksum = htons(0xffff);
> + }
> +
> + uh->udp_csum = udp_checksum;
> + }
> + } else if (proto == IPPROTO_TCP) {
> + struct tcp_header *th = dp_packet_l4(packet);
> + uint16_t old_tcp_checksum = ~th->tcp_csum;
> + uint32_t tcp_checksum = old_tcp_checksum + delta_checksum;
Add a new line here.
> + tcp_checksum = csum_finish(tcp_checksum);
> +
Remove the new line.
> + th->tcp_csum = tcp_checksum;
> + } else if (proto == IPPROTO_ICMPV6) {
> + struct icmp6_header *icmp = dp_packet_l4(packet);
> + uint16_t old_icmp_checksum = ~icmp->icmp6_cksum;
Keep name consistency, so I would call it old_icmp6_checksum.
> + uint32_t icmp6_checksum = old_icmp_checksum + delta_checksum;
Add a new line here.
> + icmp6_checksum = csum_finish(icmp6_checksum);
> +
Remove the new line.
> + icmp->icmp6_cksum = icmp6_checksum;
> + }
> + }
> + /* Write back the modified IPv6 addresses. */
> + _mm512_mask_storeu_epi64((void *) nh, 0x1F, v_new_hdr);
> + }
> +}
> +#endif
As the #if is way out of sight, I would make this +#endif /* HAVE_AVX512VBMI */
> +
> static void
> action_avx512_set_masked(struct dp_packet_batch *batch, const struct nlattr
> *a)
> {
> @@ -514,6 +683,13 @@ action_avx512_init(struct odp_execute_action_impl *self
> OVS_UNUSED)
> impl_set_masked_funcs[OVS_KEY_ATTR_ETHERNET] =
> action_avx512_eth_set_addrs;
> impl_set_masked_funcs[OVS_KEY_ATTR_IPV4] = action_avx512_ipv4_set_addrs;
>
> +#if HAVE_AVX512VBMI
> + if (action_avx512vbmi_isa_probe()) {
> + impl_set_masked_funcs[OVS_KEY_ATTR_IPV6] =
> + action_avx512_ipv6_set_addrs;
> + }
> +#endif
> +
> return 0;
> }
>
> diff --git a/lib/odp-execute-private.c b/lib/odp-execute-private.c
> index f80ae5a23..ff29e116f 100644
> --- a/lib/odp-execute-private.c
> +++ b/lib/odp-execute-private.c
> @@ -60,6 +60,23 @@ action_avx512_isa_probe(void)
>
> #endif
>
> +#if ACTION_IMPL_AVX512_CHECK && HAVE_AVX512VBMI
> +bool
> +action_avx512vbmi_isa_probe(void)
> +{
> + if (!cpu_has_isa(OVS_CPU_ISA_X86_AVX512VBMI)) {
> + return false;
> + }
> + return true;
> +}
just a nit, but I would make this as follows:
bool
action_avx512vbmi_isa_probe(void)
{
if (cpu_has_isa(OVS_CPU_ISA_X86_AVX512VBMI)) {
return true;
}
return false;
}
> +#else
> +bool
> +action_avx512vbmi_isa_probe(void)
> +{
> + return false;
> +}
> +#endif
> +
> static struct odp_execute_action_impl action_impls[] = {
> [ACTION_IMPL_AUTOVALIDATOR] = {
> .available = false,
> diff --git a/lib/odp-execute-private.h b/lib/odp-execute-private.h
> index 940180c99..643f41c2a 100644
> --- a/lib/odp-execute-private.h
> +++ b/lib/odp-execute-private.h
> @@ -78,6 +78,7 @@ BUILD_ASSERT_DECL(ACTION_IMPL_AUTOVALIDATOR == 1);
> #define ACTION_IMPL_BEGIN (ACTION_IMPL_AUTOVALIDATOR + 1)
>
> bool action_avx512_isa_probe(void);
> +bool action_avx512vbmi_isa_probe(void);
>
> /* Odp execute init handles setting up the state of the actions functions at
> * initialization time. It cannot return errors, as it must always succeed in
> --
> 2.25.1
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