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Date:   Wed, 16 May 2018 15:04:08 +0100
From:   Roman Gushchin <guro@fb.com>
To:     Mike Rapoport <rppt@linux.vnet.ibm.com>
CC:     Shuah Khan <shuah@kernel.org>, Tejun Heo <tj@kernel.org>,
        <linux-kselftest@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] selftests: cgroup: memcontrol: add basic test for socket
 accounting
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Hi Mike!

On Wed, May 16, 2018 at 02:28:09PM +0300, Mike Rapoport wrote:
> The test verifies that with active TCP traffic memory.current and
> memory.stat.sock have similar values.
> 
> Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
> ---
>  tools/testing/selftests/cgroup/test_memcontrol.c | 184 +++++++++++++++++++++++
>  1 file changed, 184 insertions(+)
> 
> diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c
> index beae06c9c899..0efdb1009175 100644
> --- a/tools/testing/selftests/cgroup/test_memcontrol.c
> +++ b/tools/testing/selftests/cgroup/test_memcontrol.c
> @@ -9,6 +9,12 @@
>  #include <sys/stat.h>
>  #include <sys/types.h>
>  #include <unistd.h>
> +#include <sys/socket.h>
> +#include <sys/wait.h>
> +#include <arpa/inet.h>
> +#include <netinet/in.h>
> +#include <netdb.h>
> +#include <errno.h>
>  
>  #include "../kselftest.h"
>  #include "cgroup_util.h"
> @@ -772,6 +778,183 @@ static int test_memcg_oom_events(const char *root)
>  	return ret;
>  }
>  
> +struct tcp_server_args {
> +	unsigned short port;
> +	int ctl[2];
> +};
> +
> +static int tcp_server(const char *cgroup, void *arg)
> +{
> +	struct tcp_server_args *srv_args = arg;
> +	struct sockaddr_in6 saddr = { 0 };
> +	socklen_t slen = sizeof(saddr);
> +	int sk, client_sk, ctl_fd, yes = 1, ret = -1;
> +
> +	close(srv_args->ctl[0]);
> +	ctl_fd = srv_args->ctl[1];
> +
> +	saddr.sin6_family = AF_INET6;
> +	saddr.sin6_addr = in6addr_any;
> +	saddr.sin6_port = htons(srv_args->port);
> +
> +	sk = socket(AF_INET6, SOCK_STREAM, 0);
> +	if (sk < 0)
> +		return ret;
> +
> +	if (setsockopt(sk, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0)
> +		goto cleanup;
> +
> +	if (bind(sk, (struct sockaddr *)&saddr, slen)) {
> +		write(ctl_fd, &errno, sizeof(errno));
> +		goto cleanup;
> +	}
> +
> +	if (listen(sk, 1))
> +		goto cleanup;
> +
> +	ret = 0;
> +	if (write(ctl_fd, &ret, sizeof(ret)) != sizeof(ret)) {
> +		ret = -1;
> +		goto cleanup;
> +	}
> +
> +	client_sk = accept(sk, NULL, NULL);
> +	if (client_sk < 0)
> +		goto cleanup;
> +
> +	ret = -1;
> +	for (;;) {
> +		uint8_t buf[0x100000];
> +
> +		if (write(client_sk, buf, sizeof(buf)) <= 0) {
> +			if (errno == ECONNRESET)
> +				ret = 0;
> +			break;
> +		}
> +	}
> +
> +	close(client_sk);
> +
> +cleanup:
> +	close(sk);
> +	return ret;
> +}
> +
> +static int tcp_client(const char *cgroup, unsigned short port)
> +{
> +	const char server[] = "localhost";
> +	struct addrinfo *ai;
> +	char servport[6];
> +	int retries = 0x10; /* nice round number */
> +	int sk, ret;
> +
> +	snprintf(servport, sizeof(servport), "%hd", port);
> +	ret = getaddrinfo(server, servport, NULL, &ai);
> +	if (ret)
> +		return ret;
> +
> +	sk = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
> +	if (sk < 0)
> +		goto free_ainfo;
> +
> +	ret = connect(sk, ai->ai_addr, ai->ai_addrlen);
> +	if (ret < 0)
> +		goto close_sk;
> +
> +	ret = KSFT_FAIL;
> +	while (retries--) {
> +		uint8_t buf[0x100000];
> +		long current, sock;
> +
> +		if (read(sk, buf, sizeof(buf)) <= 0)
> +			goto close_sk;
> +
> +		current = cg_read_long(cgroup, "memory.current");
> +		if (current < 0)
> +			goto close_sk;
> +
> +		sock = cg_read_key_long(cgroup, "memory.stat", "sock ");
> +		if (sock < 0)
> +			goto close_sk;
> +
> +		if (values_close(current, sock, 3)) {
> +			ret = KSFT_PASS;
> +			break;
> +		}

The test is flapping (at least on my dev machine) because of this condition.

I believe it's because of the batching we're using on the page charge path.
So, in theory, it should be possible to calculate the maximum difference
like num_cpus * PAGE_SIZE * batch_size.

Alternatively, just bump allowed error percentage :)

> +	}
> +
> +close_sk:
> +	close(sk);

It would be great to check that sock and current are getting 0 values
after we're closing the socket.


Thanks!