On 22 Nov 2022, at 16:10, Finn, Emma wrote:
>> -----Original Message----- >> From: Eelco Chaudron <[email protected]> >> Sent: Thursday 17 November 2022 09:21 >> To: Finn, Emma <[email protected]> >> Cc: [email protected]; [email protected]; >> [email protected] >> Subject: Re: [ovs-dev] [v3] odp-execute: Add ISA implementation of >> set_masked IPv6 action >> >> 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 >> > > Thanks for the review Eelco. Sure, I will clean up and change all the style > related comments. > Some other replies inline below. See inline comments below… >>> --- >>> 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; >> > Sure I will tidy this up. The above line will need to have cast around > old_delta though. > Otherwise it will invert 32bits instead of 16bits of old_delta, which will > make the addition wrong. > Something like this: > uint32_t csum_delta = (uint16_t)~old_delta + new_delta; That should be fine, maybe explicitly mark the part you are interested in, saw this in other code: uint32_t csum_delta = ((uint16_t) ~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. >> > The compiler is likely already lifting that code out of the loop as it is > loop invariant. > But moving outside the loop will make it clearer, so yes will do. Thanks, it’s just my autistic brain not trusting the optimizer ;) >>> +#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? >> > Ah yes good idea. To keep the same behaviour, I think we want to bitwise-OR > the two registers (not bitwise-AND) and then check if any bits are set? > If any bit is set in src/dst mask, we need to do_checksum. > Something like this > v_dst = Loadu_si128(dst) > v_src = Loadu_si128(src) > v_or = _or_si128(v_dst, v_src) > > /* generate all ones register from cmpeq of v_zeros vs itself? */ > v_zeros = _setzero_si128() > v_all_ones = _cmpeq_epi(v_zeros, v_zeros); > int do_checksum = _mm_test_all_zeros(v_or, v_all_ones); > > Does this approach make sense to you? Yes perfectly, I was not aware of the _mm_test_all_zeros() which saves the popcount ;) One comment here is that do_checksum should be a bool type, something like bool do_checksum = !!_mm_test_all_zeros(v_or, v_all_ones); >>> + 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 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
