netdev - Re: [bpf-next PATCH v2 3/7] bpf: sockmap sample, use fork() for send and recv

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Date:   Thu, 11 Jan 2018 13:08:53 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     John Fastabend <john.fastabend@...il.com>
CC:     <borkmann@...earbox.net>, <ast@...nel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [bpf-next PATCH v2 3/7] bpf: sockmap sample, use fork() for send
 and recv

On Wed, Jan 10, 2018 at 10:39:37AM -0800, John Fastabend wrote:
> Currently for SENDMSG tests first send completes then recv runs. This
> does not work well for large data sizes and/or many iterations. So
> fork the recv and send handler so that we run both send and recv. In
> the future we can add a parameter to do more than a single fork of
> tx/rx.
> 
> With this we can get many GBps of data which helps exercise the
> sockmap code.
> 
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---
>  samples/sockmap/Makefile       |    2 +
>  samples/sockmap/sockmap_user.c |   58 +++++++++++++++++++++++++++++-----------
>  2 files changed, 43 insertions(+), 17 deletions(-)
> 
> diff --git a/samples/sockmap/Makefile b/samples/sockmap/Makefile
> index 73f1da4..4fefd66 100644
> --- a/samples/sockmap/Makefile
> +++ b/samples/sockmap/Makefile
> @@ -8,7 +8,7 @@ HOSTCFLAGS += -I$(objtree)/usr/include
>  HOSTCFLAGS += -I$(srctree)/tools/lib/
>  HOSTCFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
>  HOSTCFLAGS += -I$(srctree)/tools/lib/ -I$(srctree)/tools/include
> -HOSTCFLAGS += -I$(srctree)/tools/perf
> +HOSTCFLAGS += -I$(srctree)/tools/perf -g
>  
>  sockmap-objs := ../bpf/bpf_load.o $(LIBBPF) sockmap_user.o
>  
> diff --git a/samples/sockmap/sockmap_user.c b/samples/sockmap/sockmap_user.c
> index 2d51672..48fa09a 100644
> --- a/samples/sockmap/sockmap_user.c
> +++ b/samples/sockmap/sockmap_user.c
> @@ -23,6 +23,7 @@
>  #include <stdbool.h>
>  #include <signal.h>
>  #include <fcntl.h>
> +#include <sys/wait.h>
>  
>  #include <sys/time.h>
>  #include <sys/types.h>
> @@ -197,7 +198,7 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
>  {
>  	struct msghdr msg = {0};
>  	struct iovec *iov;
> -	int i, flags = 0;
> +	int i, flags = MSG_NOSIGNAL;
>  
>  	iov = calloc(iov_count, sizeof(struct iovec));
>  	if (!iov)
> @@ -272,25 +273,50 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
>  
>  static int sendmsg_test(int iov_count, int iov_buf, int cnt, int verbose)
>  {
> +	int txpid, rxpid, err = 0;
>  	struct msg_stats s = {0};
> -	int err;
> -
> -	err = msg_loop(c1, iov_count, iov_buf, cnt, &s, true);
> -	if (err) {
> -		fprintf(stderr,
> -			"msg_loop_tx: iov_count %i iov_buf %i cnt %i err %i\n",
> -			iov_count, iov_buf, cnt, err);
> -		return err;
> +	int status;
> +
> +	errno = 0;
> +
> +	rxpid = fork();
> +	if (rxpid == 0) {
> +		err = msg_loop(p2, iov_count, iov_buf, cnt, &s, false);
> +		if (err)
> +			fprintf(stderr,
> +				"msg_loop_rx: iov_count %i iov_buf %i cnt %i err %i\n",
> +				iov_count, iov_buf, cnt, err);
> +		fprintf(stdout, "rx_sendmsg: TX_bytes %zu RX_bytes %zu\n",
> +			s.bytes_sent, s.bytes_recvd);
> +		shutdown(p2, SHUT_RDWR);
> +		shutdown(p1, SHUT_RDWR);
> +		exit(1);
> +	} else if (rxpid == -1) {
> +		perror("msg_loop_rx: ");
> +		err = errno;
Bail out here instead of continuing the tx side?

>  	}
>  
> -	msg_loop(p2, iov_count, iov_buf, cnt, &s, false);
> -	if (err)
> -		fprintf(stderr,
> -			"msg_loop_rx: iov_count %i iov_buf %i cnt %i err %i\n",
> -			iov_count, iov_buf, cnt, err);
> +	txpid = fork();
> +	if (txpid == 0) {
> +		err = msg_loop(c1, iov_count, iov_buf, cnt, &s, true);
> +		if (err)
> +			fprintf(stderr,
> +				"msg_loop_tx: iov_count %i iov_buf %i cnt %i err %i\n",
> +				iov_count, iov_buf, cnt, err);
> +		fprintf(stdout, "tx_sendmsg: TX_bytes %zu RX_bytes %zu\n",
> +			s.bytes_sent, s.bytes_recvd);
> +		shutdown(c1, SHUT_RDWR);
> +		exit(1);
> +	} else if (txpid == -1) {
> +		perror("msg_loop_tx: ");
> +		return errno;
> +	}
>  
> -	fprintf(stdout, "sendmsg: TX_bytes %zu RX_bytes %zu\n",
> -		s.bytes_sent, s.bytes_recvd);
> +	assert(waitpid(rxpid, &status, 0) == rxpid);
> +	if (!txpid)
> +		goto out;
> +	assert(waitpid(txpid, &status, 0) == txpid);
> +out:
>  	return err;
>  }
>  
>