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Date: Sun, 12 May 2024 21:02:40 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: zijianzhang@...edance.com,
netdev@...r.kernel.org
Cc: edumazet@...gle.com,
willemdebruijn.kernel@...il.com,
cong.wang@...edance.com,
xiaochun.lu@...edance.com,
Zijian Zhang <zijianzhang@...edance.com>
Subject: Re: [PATCH net-next v3 3/3] selftests: add MSG_ZEROCOPY msg_control
notification test
zijianzhang@ wrote:
> From: Zijian Zhang <zijianzhang@...edance.com>
>
> We update selftests/net/msg_zerocopy.c to accommodate the new mechanism.
>
> Test result from selftests/net/msg_zerocopy.c,
> cfg_notification_limit = 1, in this case MSG_ZEROCOPY approximately
> aligns with the semantics of MSG_ZEROCOPY_UARG. In this case, the new
> flag has around 13% cpu savings in TCP and 18% cpu savings in UDP.
> +---------------------+---------+---------+---------+---------+
> | Test Type / Protocol| TCP v4 | TCP v6 | UDP v4 | UDP v6 |
> +---------------------+---------+---------+---------+---------+
> | ZCopy (MB) | 5147 | 4885 | 7489 | 7854 |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy (MB) | 5859 | 5505 | 9053 | 9236 |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy / ZCopy | 113.83% | 112.69% | 120.88% | 117.59% |
> +---------------------+---------+---------+---------+---------+
>
> cfg_notification_limit = 32, it means less poll + recvmsg overhead,
> the new mechanism performs 8% better in TCP. For UDP, no obvious
> performance gain is observed and sometimes may lead to degradation.
> Thus, if users don't need to retrieve the notification ASAP in UDP,
> the original mechanism is preferred.
> +---------------------+---------+---------+---------+---------+
> | Test Type / Protocol| TCP v4 | TCP v6 | UDP v4 | UDP v6 |
> +---------------------+---------+---------+---------+---------+
> | ZCopy (MB) | 6272 | 6138 | 12138 | 10055 |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy (MB) | 6774 | 6620 | 11504 | 10355 |
> +---------------------+---------+---------+---------+---------+
> | New ZCopy / ZCopy | 108.00% | 107.85% | 94.78% | 102.98% |
> +---------------------+---------+---------+---------+---------+
>
> Signed-off-by: Zijian Zhang <zijianzhang@...edance.com>
> Signed-off-by: Xiaochun Lu <xiaochun.lu@...edance.com>
> ---
> tools/testing/selftests/net/msg_zerocopy.c | 103 ++++++++++++++++++--
> tools/testing/selftests/net/msg_zerocopy.sh | 1 +
> 2 files changed, 97 insertions(+), 7 deletions(-)
>
> diff --git a/tools/testing/selftests/net/msg_zerocopy.c b/tools/testing/selftests/net/msg_zerocopy.c
> index ba6c257f689c..48750a7a162c 100644
> --- a/tools/testing/selftests/net/msg_zerocopy.c
> +++ b/tools/testing/selftests/net/msg_zerocopy.c
> @@ -1,3 +1,4 @@
> +// SPDX-License-Identifier: GPL-2.0
> /* Evaluate MSG_ZEROCOPY
> *
> * Send traffic between two processes over one of the supported
> @@ -66,6 +67,10 @@
> #define SO_ZEROCOPY 60
> #endif
>
> +#ifndef SCM_ZC_NOTIFICATION
> +#define SCM_ZC_NOTIFICATION 78
> +#endif
> +
> #ifndef SO_EE_CODE_ZEROCOPY_COPIED
> #define SO_EE_CODE_ZEROCOPY_COPIED 1
> #endif
> @@ -74,6 +79,13 @@
> #define MSG_ZEROCOPY 0x4000000
> #endif
>
> +#define ZC_MSGERR_NOTIFICATION 1
> +#define ZC_MSGCTL_NOTIFICATION 2
Please define an enum
And consider less truncated, more descriptive, names. E.g.,
MSG_ZEROCOPY_NOTIFY_ERRQUEUE
MSG_ZEROCOPY_NOTIFY_SENDMSG
> +
> +#define SOCK_ZC_INFO_NUM 8
> +
> +#define INVALID_ZEROCOPY_VAL 2
> +
> static int cfg_cork;
> static bool cfg_cork_mixed;
> static int cfg_cpu = -1; /* default: pin to last cpu */
> @@ -86,13 +98,16 @@ static int cfg_runtime_ms = 4200;
> static int cfg_verbose;
> static int cfg_waittime_ms = 500;
> static int cfg_notification_limit = 32;
> -static bool cfg_zerocopy;
> +static int cfg_zerocopy; /* Either 1 or 2, mode for SO_ZEROCOPY */
>
> static socklen_t cfg_alen;
> static struct sockaddr_storage cfg_dst_addr;
> static struct sockaddr_storage cfg_src_addr;
>
> static char payload[IP_MAXPACKET];
> +static struct zc_info_elem zc_info[SOCK_ZC_INFO_NUM];
> +static char zc_ckbuf[CMSG_SPACE(sizeof(void *))];
> +static struct zc_info_elem *zc_info_ptr = zc_info;
> static long packets, bytes, completions, expected_completions;
> static int zerocopied = -1;
> static uint32_t next_completion;
> @@ -170,6 +185,26 @@ static int do_accept(int fd)
> return fd;
> }
>
> +static void add_zcopy_info(struct msghdr *msg)
> +{
> + int i;
> + struct cmsghdr *cm;
> +
> + if (!msg->msg_control)
> + error(1, errno, "NULL user arg");
> + cm = (void *)msg->msg_control;
> + /* Although only the address of the array will be written into the
> + * zc_ckbuf, we assign cmsg_len to CMSG_LEN(sizeof(zc_info)) to specify
> + * the length of the array.
> + */
> + cm->cmsg_len = CMSG_LEN(sizeof(zc_info));
> + cm->cmsg_level = SOL_SOCKET;
> + cm->cmsg_type = SCM_ZC_NOTIFICATION;
> + memcpy(CMSG_DATA(cm), &zc_info_ptr, sizeof(zc_info_ptr));
> + for (i = 0; i < SOCK_ZC_INFO_NUM; i++)
> + zc_info[i].zerocopy = INVALID_ZEROCOPY_VAL;
> +}
> +
> static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
> {
> struct cmsghdr *cm;
> @@ -183,7 +218,7 @@ static void add_zcopy_cookie(struct msghdr *msg, uint32_t cookie)
> memcpy(CMSG_DATA(cm), &cookie, sizeof(cookie));
> }
>
> -static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
> +static bool do_sendmsg(int fd, struct msghdr *msg, int do_zerocopy, int domain)
> {
> int ret, len, i, flags;
> static uint32_t cookie;
> @@ -201,6 +236,15 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
> msg->msg_controllen = CMSG_SPACE(sizeof(cookie));
> msg->msg_control = (struct cmsghdr *)ckbuf;
> add_zcopy_cookie(msg, ++cookie);
> + } else if (do_zerocopy == ZC_MSGCTL_NOTIFICATION) {
> + memset(&msg->msg_control, 0, sizeof(msg->msg_control));
> + /* Although only the address of the array will be written into the
> + * zc_ckbuf, msg_controllen must be larger or equal than any cmsg_len
> + * in it. Otherwise, we will get -EINVAL.
> + */
> + msg->msg_controllen = CMSG_SPACE(sizeof(zc_info));
> + msg->msg_control = (struct cmsghdr *)zc_ckbuf;
> + add_zcopy_info(msg);
> }
> }
>
> @@ -219,7 +263,7 @@ static bool do_sendmsg(int fd, struct msghdr *msg, bool do_zerocopy, int domain)
> if (do_zerocopy && ret)
> expected_completions++;
> }
> - if (do_zerocopy && domain == PF_RDS) {
> + if (msg->msg_control) {
> msg->msg_control = NULL;
> msg->msg_controllen = 0;
> }
> @@ -393,6 +437,42 @@ static bool do_recvmsg_completion(int fd)
> return ret;
> }
>
> +static void do_recv_completions2(void)
> +{
> + int i;
> + __u32 hi, lo, range;
> + __u8 zerocopy;
> +
> + for (i = 0; zc_info[i].zerocopy != INVALID_ZEROCOPY_VAL; i++) {
> + struct zc_info_elem elem = zc_info[i];
> +
> + hi = elem.hi;
> + lo = elem.lo;
> + zerocopy = elem.zerocopy;
> + range = hi - lo + 1;
> +
> + if (cfg_verbose && lo != next_completion)
> + fprintf(stderr, "gap: %u..%u does not append to %u\n",
> + lo, hi, next_completion);
> + next_completion = hi + 1;
> +
> + if (zerocopied == -1)
> + zerocopied = zerocopy;
> + else if (zerocopied != zerocopy) {
> + fprintf(stderr, "serr: inconsistent\n");
> + zerocopied = zerocopy;
> + }
> +
> + completions += range;
> +
> + if (cfg_verbose >= 2)
> + fprintf(stderr, "completed: %u (h=%u l=%u)\n",
> + range, hi, lo);
> + }
> +
> + sendmsg_counter -= i;
> +}
> +
> static bool do_recv_completion(int fd, int domain)
> {
> struct sock_extended_err *serr;
> @@ -554,11 +634,15 @@ static void do_tx(int domain, int type, int protocol)
> else
> do_sendmsg(fd, &msg, cfg_zerocopy, domain);
>
> - if (cfg_zerocopy && sendmsg_counter >= cfg_notification_limit)
> + if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION &&
> + sendmsg_counter >= cfg_notification_limit)
> do_recv_completions(fd, domain);
>
> + if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
> + do_recv_completions2();
> +
> while (!do_poll(fd, POLLOUT)) {
> - if (cfg_zerocopy)
> + if (cfg_zerocopy == ZC_MSGERR_NOTIFICATION)
> do_recv_completions(fd, domain);
> }
>
> @@ -716,7 +800,7 @@ static void parse_opts(int argc, char **argv)
>
> cfg_payload_len = max_payload_len;
>
> - while ((c = getopt(argc, argv, "46c:C:D:i:l:mp:rs:S:t:vz")) != -1) {
> + while ((c = getopt(argc, argv, "46c:C:D:i:l:mnp:rs:S:t:vz")) != -1) {
> switch (c) {
> case '4':
> if (cfg_family != PF_UNSPEC)
> @@ -750,6 +834,9 @@ static void parse_opts(int argc, char **argv)
> case 'm':
> cfg_cork_mixed = true;
> break;
> + case 'n':
> + cfg_zerocopy = ZC_MSGCTL_NOTIFICATION;
> + break;
> case 'p':
> cfg_port = strtoul(optarg, NULL, 0);
> break;
> @@ -769,7 +856,7 @@ static void parse_opts(int argc, char **argv)
> cfg_verbose++;
> break;
> case 'z':
> - cfg_zerocopy = true;
> + cfg_zerocopy = ZC_MSGERR_NOTIFICATION;
> break;
> }
> }
> @@ -780,6 +867,8 @@ static void parse_opts(int argc, char **argv)
> error(1, 0, "-D <server addr> required for PF_RDS\n");
> if (!cfg_rx && !saddr)
> error(1, 0, "-S <client addr> required for PF_RDS\n");
> + if (cfg_zerocopy == ZC_MSGCTL_NOTIFICATION)
> + error(1, 0, "PF_RDS does not support ZC_MSGCTL_NOTIFICATION");
> }
> setup_sockaddr(cfg_family, daddr, &cfg_dst_addr);
> setup_sockaddr(cfg_family, saddr, &cfg_src_addr);
> diff --git a/tools/testing/selftests/net/msg_zerocopy.sh b/tools/testing/selftests/net/msg_zerocopy.sh
> index 89c22f5320e0..022a6936d86f 100755
> --- a/tools/testing/selftests/net/msg_zerocopy.sh
> +++ b/tools/testing/selftests/net/msg_zerocopy.sh
> @@ -118,4 +118,5 @@ do_test() {
>
> do_test "${EXTRA_ARGS}"
> do_test "-z ${EXTRA_ARGS}"
> +do_test "-n ${EXTRA_ARGS}"
> echo ok
> --
> 2.20.1
>
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