Commit bd60438e authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

selftests/net: report rcv_mss in tcp_mmap 



tcp_mmap tests TCP_ZEROCOPY_RECEIVE. If 0% of data is received using
mmap, this may be due to mss. Report rcv_mss to identify this cause.

Output of a run failed due to too small mss:

    received 32768 MB (0 % mmap'ed) in 8.40458 s, 32.7057 Gbit
      cpu usage user:0.027922 sys:8.21126, 251.44 usec per MB, 3252 c-switches, rcv_mss 1428

Output on a successful run:

    received 32768 MB (99.9507 % mmap'ed) in 4.69023 s, 58.6064 Gbit
      cpu usage user:0.029172 sys:2.56105, 79.0473 usec per MB, 57591 c-switches, rcv_mss 4096

Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 27bcd122

tools/testing/selftests/net/tcp_mmap.c

+16 −2
Original line number Diff line number Diff line
@@ -153,6 +153,19 @@ static void *mmap_large_buffer(size_t need, size_t *allocated) 
	return buffer;

}



static uint32_t tcp_info_get_rcv_mss(int fd)

{

	socklen_t sz = sizeof(struct tcp_info);

	struct tcp_info info;



	if (getsockopt(fd, IPPROTO_TCP, TCP_INFO, &info, &sz)) {

		fprintf(stderr, "Error fetching TCP_INFO\n");

		return 0;

	}



	return info.tcpi_rcv_mss;

}



void *child_thread(void *arg)

{

	unsigned char digest[SHA256_DIGEST_LENGTH];
@@ -288,7 +301,7 @@ void *child_thread(void *arg) 
		total_usec = 1000000*ru.ru_utime.tv_sec + ru.ru_utime.tv_usec +

			     1000000*ru.ru_stime.tv_sec + ru.ru_stime.tv_usec;

		printf("received %lg MB (%lg %% mmap'ed) in %lg s, %lg Gbit\n"

		       "  cpu usage user:%lg sys:%lg, %lg usec per MB, %lu c-switches\n",

		       "  cpu usage user:%lg sys:%lg, %lg usec per MB, %lu c-switches, rcv_mss %u\n",

				total / (1024.0 * 1024.0),

				100.0*total_mmap/total,

				(double)delta_usec / 1000000.0,
@@ -296,7 +309,8 @@ void *child_thread(void *arg) 
				(double)ru.ru_utime.tv_sec + (double)ru.ru_utime.tv_usec / 1000000.0,

				(double)ru.ru_stime.tv_sec + (double)ru.ru_stime.tv_usec / 1000000.0,

				(double)total_usec/mb,

				ru.ru_nvcsw);

				ru.ru_nvcsw,

				tcp_info_get_rcv_mss(fd));

	}

error:

	munmap(buffer, buffer_sz);