Re: [PATCH v3 net-next 2/2] selftests: net: tcp_mmap must use TCP_ZEROCOPY_RECEIVE

[Soheil Hassas Yeganeh]

On Thu, Apr 26, 2018 at 10:50 AM, Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
> After prior kernel change, mmap() on TCP socket only reserves VMA.
>
> We have to use getsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...)
> to perform the transfert of pages from skbs in TCP receive queue into such VMA.
>
> struct tcp_zerocopy_receive {
>         __u64 address;          /* in: address of mapping */
>         __u32 length;           /* in/out: number of bytes to map/mapped */
>         __u32 recv_skip_hint;   /* out: amount of bytes to skip */
> };
>
> After a successful getsockopt(...TCP_ZEROCOPY_RECEIVE...), @length contains
> number of bytes that were mapped, and @recv_skip_hint contains number of bytes
> that should be read using conventional read()/recv()/recvmsg() system calls,
> to skip a sequence of bytes that can not be mapped, because not properly page
> aligned.
>
> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>

Acked-by: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>

Thank you, again!

> ---
>  tools/testing/selftests/net/tcp_mmap.c | 64 +++++++++++++++-----------
>  1 file changed, 37 insertions(+), 27 deletions(-)
>
> diff --git a/tools/testing/selftests/net/tcp_mmap.c b/tools/testing/selftests/net/tcp_mmap.c
> index dea342fe6f4e88b5709d2ac37b2fc9a2a320bf44..77f762780199ff1f69f9f6b3f18e72deddb69f5e 100644
> --- a/tools/testing/selftests/net/tcp_mmap.c
> +++ b/tools/testing/selftests/net/tcp_mmap.c
> @@ -76,9 +76,10 @@
>  #include <time.h>
>  #include <sys/time.h>
>  #include <netinet/in.h>
> -#include <netinet/tcp.h>
>  #include <arpa/inet.h>
>  #include <poll.h>
> +#include <linux/tcp.h>
> +#include <assert.h>
>
>  #ifndef MSG_ZEROCOPY
>  #define MSG_ZEROCOPY    0x4000000
> @@ -134,11 +135,12 @@ void hash_zone(void *zone, unsigned int length)
>  void *child_thread(void *arg)
>  {
>         unsigned long total_mmap = 0, total = 0;
> +       struct tcp_zerocopy_receive zc;
>         unsigned long delta_usec;
>         int flags = MAP_SHARED;
>         struct timeval t0, t1;
>         char *buffer = NULL;
> -       void *oaddr = NULL;
> +       void *addr = NULL;
>         double throughput;
>         struct rusage ru;
>         int lu, fd;
> @@ -153,41 +155,46 @@ void *child_thread(void *arg)
>                 perror("malloc");
>                 goto error;
>         }
> +       if (zflg) {
> +               addr = mmap(NULL, chunk_size, PROT_READ, flags, fd, 0);
> +               if (addr == (void *)-1)
> +                       zflg = 0;
> +       }
>         while (1) {
>                 struct pollfd pfd = { .fd = fd, .events = POLLIN, };
>                 int sub;
>
>                 poll(&pfd, 1, 10000);
>                 if (zflg) {
> -                       void *naddr;
> +                       socklen_t zc_len = sizeof(zc);
> +                       int res;
>
> -                       naddr = mmap(oaddr, chunk_size, PROT_READ, flags, fd, 0);
> -                       if (naddr == (void *)-1) {
> -                               if (errno == EAGAIN) {
> -                                       /* That is if SO_RCVLOWAT is buggy */
> -                                       usleep(1000);
> -                                       continue;
> -                               }
> -                               if (errno == EINVAL) {
> -                                       flags = MAP_SHARED;
> -                                       oaddr = NULL;
> -                                       goto fallback;
> -                               }
> -                               if (errno != EIO)
> -                                       perror("mmap()");
> +                       zc.address = (__u64)addr;
> +                       zc.length = chunk_size;
> +                       zc.recv_skip_hint = 0;
> +                       res = getsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE,
> +                                        &zc, &zc_len);
> +                       if (res == -1)
>                                 break;
> +
> +                       if (zc.length) {
> +                               assert(zc.length <= chunk_size);
> +                               total_mmap += zc.length;
> +                               if (xflg)
> +                                       hash_zone(addr, zc.length);
> +                               total += zc.length;
>                         }
> -                       total_mmap += chunk_size;
> -                       if (xflg)
> -                               hash_zone(naddr, chunk_size);
> -                       total += chunk_size;
> -                       if (!keepflag) {
> -                               flags |= MAP_FIXED;
> -                               oaddr = naddr;
> +                       if (zc.recv_skip_hint) {
> +                               assert(zc.recv_skip_hint <= chunk_size);
> +                               lu = read(fd, buffer, zc.recv_skip_hint);
> +                               if (lu > 0) {
> +                                       if (xflg)
> +                                               hash_zone(buffer, lu);
> +                                       total += lu;
> +                               }
>                         }
>                         continue;
>                 }
> -fallback:
>                 sub = 0;
>                 while (sub < chunk_size) {
>                         lu = read(fd, buffer + sub, chunk_size - sub);
> @@ -228,6 +235,8 @@ void *child_thread(void *arg)
>  error:
>         free(buffer);
>         close(fd);
> +       if (zflg)
> +               munmap(addr, chunk_size);
>         pthread_exit(0);
>  }
>
> @@ -371,7 +380,8 @@ int main(int argc, char *argv[])
>                 setup_sockaddr(cfg_family, host, &listenaddr);
>
>                 if (mss &&
> -                   setsockopt(fdlisten, SOL_TCP, TCP_MAXSEG, &mss, sizeof(mss)) == -1) {
> +                   setsockopt(fdlisten, IPPROTO_TCP, TCP_MAXSEG,
> +                              &mss, sizeof(mss)) == -1) {
>                         perror("setsockopt TCP_MAXSEG");
>                         exit(1);
>                 }
> @@ -402,7 +412,7 @@ int main(int argc, char *argv[])
>         setup_sockaddr(cfg_family, host, &addr);
>
>         if (mss &&
> -           setsockopt(fd, SOL_TCP, TCP_MAXSEG, &mss, sizeof(mss)) == -1) {
> +           setsockopt(fd, IPPROTO_TCP, TCP_MAXSEG, &mss, sizeof(mss)) == -1) {
>                 perror("setsockopt TCP_MAXSEG");
>                 exit(1);
>         }
> --
> 2.17.0.484.g0c8726318c-goog
>