[PATCH] per task delay accounting taskstats interface: documentation fix

 *

 * Copyright (C) Shailabh Nagar, IBM Corp. 2005

 * Copyright (C) Balbir Singh, IBM Corp. 2006

 * Copyright (c) Jay Lan, SGI. 2006

 *

 */

#define err(code, fmt, arg...) do { printf(fmt, ##arg); exit(code); } while (0)

int done = 0;

int rcvbufsz=0;

    char name[100];

int dbg=0, print_delays=0;

__u64 stime, utime;

#define PRINTF(fmt, arg...) {			\

	    if (dbg) {				\

		printf(fmt, ##arg);		\

	    }					\

	}

/* Maximum size of response requested or message sent */

#define MAX_MSG_SIZE	256

/* Maximum number of cpus expected to be specified in a cpumask */

#define MAX_CPUS	32

/* Maximum length of pathname to log file */

#define MAX_FILENAME	256

struct msgtemplate {

	struct nlmsghdr n;

	struct genlmsghdr g;

	char buf[MAX_MSG_SIZE];

};

char cpumask[100+6*MAX_CPUS];

/*

 * Create a raw netlink socket and bind

 */

static int create_nl_socket(int protocol, int groups)

static int create_nl_socket(int protocol)

{

    socklen_t addr_len;

	int fd;

	struct sockaddr_nl local;

	if (fd < 0)

		return -1;

	if (rcvbufsz)

		if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF,

				&rcvbufsz, sizeof(rcvbufsz)) < 0) {

			printf("Unable to set socket rcv buf size to %d\n",

			       rcvbufsz);

			return -1;

		}

	memset(&local, 0, sizeof(local));

	local.nl_family = AF_NETLINK;

    local.nl_groups = groups;

	if (bind(fd, (struct sockaddr *) &local, sizeof(local)) < 0)

		goto error;

	return -1;

}

int sendto_fd(int s, const char *buf, int bufLen)

int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid,

	     __u8 genl_cmd, __u16 nla_type,

	     void *nla_data, int nla_len)

{

	struct nlattr *na;

	struct sockaddr_nl nladdr;

    int r;

	int r, buflen;

	char *buf;

	struct msgtemplate msg;

	msg.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);

	msg.n.nlmsg_type = nlmsg_type;

	msg.n.nlmsg_flags = NLM_F_REQUEST;

	msg.n.nlmsg_seq = 0;

	msg.n.nlmsg_pid = nlmsg_pid;

	msg.g.cmd = genl_cmd;

	msg.g.version = 0x1;

	na = (struct nlattr *) GENLMSG_DATA(&msg);

	na->nla_type = nla_type;

	na->nla_len = nla_len + 1 + NLA_HDRLEN;

	memcpy(NLA_DATA(na), nla_data, nla_len);

	msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);

	buf = (char *) &msg;

	buflen = msg.n.nlmsg_len ;

	memset(&nladdr, 0, sizeof(nladdr));

	nladdr.nl_family = AF_NETLINK;

    while ((r = sendto(s, buf, bufLen, 0, (struct sockaddr *) &nladdr,

		       sizeof(nladdr))) < bufLen) {

	while ((r = sendto(sd, buf, buflen, 0, (struct sockaddr *) &nladdr,

			   sizeof(nladdr))) < buflen) {

		if (r > 0) {

			buf += r;

	    bufLen -= r;

			buflen -= r;

		} else if (errno != EAGAIN)

			return -1;

	}

	return 0;

}

/*

 * Probe the controller in genetlink to find the family id

 * for the TASKSTATS family

 */

int get_family_id(int sd)

{

    struct {

	struct nlmsghdr n;

	struct genlmsghdr g;

	char buf[256];

    } family_req;

	struct {

		struct nlmsghdr n;

		struct genlmsghdr g;

		char buf[256];

	} ans;

    int id;

	int id, rc;

	struct nlattr *na;

	int rep_len;

    /* Get family name */

    family_req.n.nlmsg_type = GENL_ID_CTRL;

    family_req.n.nlmsg_flags = NLM_F_REQUEST;

    family_req.n.nlmsg_seq = 0;

    family_req.n.nlmsg_pid = getpid();

    family_req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);

    family_req.g.cmd = CTRL_CMD_GETFAMILY;

    family_req.g.version = 0x1;

    na = (struct nlattr *) GENLMSG_DATA(&family_req);

    na->nla_type = CTRL_ATTR_FAMILY_NAME;

    na->nla_len = strlen(TASKSTATS_GENL_NAME) + 1 + NLA_HDRLEN;

    strcpy(NLA_DATA(na), TASKSTATS_GENL_NAME);

    family_req.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);

    if (sendto_fd(sd, (char *) &family_req, family_req.n.nlmsg_len) < 0)

	err(1, "error sending message via Netlink\n");

	strcpy(name, TASKSTATS_GENL_NAME);

	rc = send_cmd(sd, GENL_ID_CTRL, getpid(), CTRL_CMD_GETFAMILY,

			CTRL_ATTR_FAMILY_NAME, (void *)name,

			strlen(TASKSTATS_GENL_NAME)+1);

	rep_len = recv(sd, &ans, sizeof(ans), 0);

    if (rep_len < 0)

	err(1, "error receiving reply message via Netlink\n");

    /* Validate response message */

    if (!NLMSG_OK((&ans.n), rep_len))

	err(1, "invalid reply message received via Netlink\n");

    if (ans.n.nlmsg_type == NLMSG_ERROR) {	/* error */

	printf("error received NACK - leaving\n");

	exit(1);

    }

	if (ans.n.nlmsg_type == NLMSG_ERROR ||

	    (rep_len < 0) || !NLMSG_OK((&ans.n), rep_len))

		return 0;

	na = (struct nlattr *) GENLMSG_DATA(&ans);

	na = (struct nlattr *) ((char *) na + NLA_ALIGN(na->nla_len));

	return id;

}

void print_taskstats(struct taskstats *t)

void print_delayacct(struct taskstats *t)

{

	printf("\n\nCPU   %15s%15s%15s%15s\n"

	       "      %15llu%15llu%15llu%15llu\n"

	       "count", "delay total", t->swapin_count, t->swapin_delay_total);

}

void sigchld(int sig)

{

    done = 1;

}

int main(int argc, char *argv[])

{

    int rc;

    int sk_nl;

    struct nlmsghdr *nlh;

    struct genlmsghdr *genlhdr;

    char *buf;

    struct taskstats_cmd_param *param;

	int c, rc, rep_len, aggr_len, len2, cmd_type;

	__u16 id;

    struct nlattr *na;

    /* For receiving */

    struct sockaddr_nl kern_nla, from_nla;

    socklen_t from_nla_len;

    int recv_len;

    struct taskstats_reply *reply;

    struct {

	struct nlmsghdr n;

	struct genlmsghdr g;

	char buf[256];

    } req;

    struct {

	struct nlmsghdr n;

	struct genlmsghdr g;

	char buf[256];

    } ans;

	__u32 mypid;

	struct nlattr *na;

	int nl_sd = -1;

    int rep_len;

	int len = 0;

    int aggr_len, len2;

    struct sockaddr_nl nladdr;

	pid_t tid = 0;

	pid_t rtid = 0;

    int cmd_type = TASKSTATS_TYPE_TGID;

    int c, status;

    int forking = 0;

    struct sigaction act = {

	.sa_handler = SIG_IGN,

	.sa_mask = SA_NOMASK,

    };

    struct sigaction tact ;

    if (argc < 3) {

	printf("usage %s [-t tgid][-p pid][-c cmd]\n", argv[0]);

	exit(-1);

    }

	int fd = 0;

	int count = 0;

	int write_file = 0;

	int maskset = 0;

	char logfile[128];

	int loop = 0;

    tact.sa_handler = sigchld;

    sigemptyset(&tact.sa_mask);

    if (sigaction(SIGCHLD, &tact, NULL) < 0)

	err(1, "sigaction failed for SIGCHLD\n");

	struct msgtemplate msg;

	while (1) {

	c = getopt(argc, argv, "t:p:c:");

		c = getopt(argc, argv, "dw:r:m:t:p:v:l");

		if (c < 0)

			break;

		switch (c) {

		case 'd':

			printf("print delayacct stats ON\n");

			print_delays = 1;

			break;

		case 'w':

			strncpy(logfile, optarg, MAX_FILENAME);

			printf("write to file %s\n", logfile);

			write_file = 1;

			break;

		case 'r':

			rcvbufsz = atoi(optarg);

			printf("receive buf size %d\n", rcvbufsz);

			if (rcvbufsz < 0)

				err(1, "Invalid rcv buf size\n");

			break;

		case 'm':

			strncpy(cpumask, optarg, sizeof(cpumask));

			maskset = 1;

			printf("cpumask %s maskset %d\n", cpumask, maskset);

			break;

		case 't':

			tid = atoi(optarg);

			if (!tid)

				err(1, "Invalid tgid\n");

			cmd_type = TASKSTATS_CMD_ATTR_TGID;

			print_delays = 1;

			break;

		case 'p':

			tid = atoi(optarg);

			if (!tid)

				err(1, "Invalid pid\n");

	    cmd_type = TASKSTATS_CMD_ATTR_TGID;

			cmd_type = TASKSTATS_CMD_ATTR_PID;

			print_delays = 1;

			break;

	case 'c':

	    opterr = 0;

	    tid = fork();

	    if (tid < 0)

		err(1, "fork failed\n");

	    if (tid == 0) {	/* child process */

		if (execvp(argv[optind - 1], &argv[optind - 1]) < 0) {

		    exit(-1);

		}

	    }

	    forking = 1;

		case 'v':

			printf("debug on\n");

			dbg = 1;

			break;

		case 'l':

			printf("listen forever\n");

			loop = 1;

			break;

		default:

	    printf("usage %s [-t tgid][-p pid][-c cmd]\n", argv[0]);

			printf("Unknown option %d\n", c);

			exit(-1);

	    break;

		}

	if (c == 'c')

	    break;

	}

    /* Construct Netlink request message */

    /* Send Netlink request message & get reply */

	if (write_file) {

		fd = open(logfile, O_WRONLY | O_CREAT | O_TRUNC,

			  S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

		if (fd == -1) {

			perror("Cannot open output file\n");

			exit(1);

		}

	}

    if ((nl_sd =

	 create_nl_socket(NETLINK_GENERIC, TASKSTATS_LISTEN_GROUP)) < 0)

	if ((nl_sd = create_nl_socket(NETLINK_GENERIC)) < 0)

		err(1, "error creating Netlink socket\n");

	mypid = getpid();

	id = get_family_id(nl_sd);

	if (!id) {

		printf("Error getting family id, errno %d", errno);

		goto err;

	}

	PRINTF("family id %d\n", id);

	if (maskset) {

		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,

			      TASKSTATS_CMD_ATTR_REGISTER_CPUMASK,

			      &cpumask, sizeof(cpumask));

		PRINTF("Sent register cpumask, retval %d\n", rc);

		if (rc < 0) {

			printf("error sending register cpumask\n");

			goto err;

		}

	}

    /* Send command needed */

    req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);

    req.n.nlmsg_type = id;

    req.n.nlmsg_flags = NLM_F_REQUEST;

    req.n.nlmsg_seq = 0;

    req.n.nlmsg_pid = tid;

    req.g.cmd = TASKSTATS_CMD_GET;

    na = (struct nlattr *) GENLMSG_DATA(&req);

    na->nla_type = cmd_type;

    na->nla_len = sizeof(unsigned int) + NLA_HDRLEN;

    *(__u32 *) NLA_DATA(na) = tid;

    req.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);

    if (!forking && sendto_fd(nl_sd, (char *) &req, req.n.nlmsg_len) < 0)

	err(1, "error sending message via Netlink\n");

    act.sa_handler = SIG_IGN;

    sigemptyset(&act.sa_mask);

    if (sigaction(SIGINT, &act, NULL) < 0)

	err(1, "sigaction failed for SIGINT\n");

	if (tid) {

		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,

			      cmd_type, &tid, sizeof(__u32));

		PRINTF("Sent pid/tgid, retval %d\n", rc);

		if (rc < 0) {

			printf("error sending tid/tgid cmd\n");

			goto done;

		}

	}

	do {

		int i;

	struct pollfd pfd;

	int pollres;

	pfd.events = 0xffff & ~POLLOUT;

	pfd.fd = nl_sd;

	pollres = poll(&pfd, 1, 5000);

	if (pollres < 0 || done) {

	    break;

	}

	rep_len = recv(nl_sd, &ans, sizeof(ans), 0);

	nladdr.nl_family = AF_NETLINK;

	nladdr.nl_groups = TASKSTATS_LISTEN_GROUP;

	if (ans.n.nlmsg_type == NLMSG_ERROR) {	/* error */

	    printf("error received NACK - leaving\n");

	    exit(1);

	}

		rep_len = recv(nl_sd, &msg, sizeof(msg), 0);

		PRINTF("received %d bytes\n", rep_len);

		if (rep_len < 0) {

	    err(1, "error receiving reply message via Netlink\n");

	    break;

			printf("nonfatal reply error: errno %d\n", errno);

			continue;

		}

		if (msg.n.nlmsg_type == NLMSG_ERROR ||

		    !NLMSG_OK((&msg.n), rep_len)) {

			printf("fatal reply error,  errno %d\n", errno);

			goto done;

		}

	/* Validate response message */

	if (!NLMSG_OK((&ans.n), rep_len))

	    err(1, "invalid reply message received via Netlink\n");

		PRINTF("nlmsghdr size=%d, nlmsg_len=%d, rep_len=%d\n",

		       sizeof(struct nlmsghdr), msg.n.nlmsg_len, rep_len);

	rep_len = GENLMSG_PAYLOAD(&ans.n);

	na = (struct nlattr *) GENLMSG_DATA(&ans);

		rep_len = GENLMSG_PAYLOAD(&msg.n);

		na = (struct nlattr *) GENLMSG_DATA(&msg);

		len = 0;

		i = 0;

		while (len < rep_len) {

			len += NLA_ALIGN(na->nla_len);

			switch (na->nla_type) {

	    case TASKSTATS_TYPE_AGGR_PID:

		/* Fall through */

			case TASKSTATS_TYPE_AGGR_TGID:

				/* Fall through */

			case TASKSTATS_TYPE_AGGR_PID:

				aggr_len = NLA_PAYLOAD(na->nla_len);

				len2 = 0;

				/* For nested attributes, na follows */

					switch (na->nla_type) {

					case TASKSTATS_TYPE_PID:

						rtid = *(int *) NLA_DATA(na);

						if (print_delays)

							printf("PID\t%d\n", rtid);

						break;

					case TASKSTATS_TYPE_TGID:

						rtid = *(int *) NLA_DATA(na);

						if (print_delays)

							printf("TGID\t%d\n", rtid);

						break;

					case TASKSTATS_TYPE_STATS:

			if (rtid == tid) {

			    print_taskstats((struct taskstats *)

					    NLA_DATA(na));

			    done = 1;

						count++;

						if (print_delays)

							print_delayacct((struct taskstats *) NLA_DATA(na));

						if (fd) {

							if (write(fd, NLA_DATA(na), na->nla_len) < 0) {

								err(1,"write error\n");

							}

						}

						if (!loop)

							goto done;

						break;

					default:

						printf("Unknown nested nla_type %d\n", na->nla_type);

						break;

					}

					len2 += NLA_ALIGN(na->nla_len);

					na = (struct nlattr *) ((char *) na + len2);

		    if (done)

			break;

		}

				}

	    na = (struct nlattr *) (GENLMSG_DATA(&ans) + len);

	    if (done)

				break;

	}

	if (done)

			default:

				printf("Unknown nla_type %d\n", na->nla_type);

				break;

			}

    while (1);

			na = (struct nlattr *) (GENLMSG_DATA(&msg) + len);

		}

	} while (loop);

done:

	if (maskset) {

		rc = send_cmd(nl_sd, id, mypid, TASKSTATS_CMD_GET,

			      TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK,

			      &cpumask, sizeof(cpumask));

		printf("Sent deregister mask, retval %d\n", rc);

		if (rc < 0)

			err(rc, "error sending deregister cpumask\n");

	}

err:

	close(nl_sd);

	if (fd)

		close(fd);

	return 0;

}

Usage

-----

To get statistics during task's lifetime, userspace opens a unicast netlink

To get statistics during a task's lifetime, userspace opens a unicast netlink

socket (NETLINK_GENERIC family) and sends commands specifying a pid or a tgid.

The response contains statistics for a task (if pid is specified) or the sum of

statistics for all tasks of the process (if tgid is specified).

To obtain statistics for tasks which are exiting, userspace opens a multicast

netlink socket. Each time a task exits, its per-pid statistics is always sent

by the kernel to each listener on the multicast socket. In addition, if it is

the last thread exiting its thread group, an additional record containing the

per-tgid stats are also sent. The latter contains the sum of per-pid stats for

all threads in the thread group, both past and present.

To obtain statistics for tasks which are exiting, the userspace listener

sends a register command and specifies a cpumask. Whenever a task exits on

one of the cpus in the cpumask, its per-pid statistics are sent to the

registered listener. Using cpumasks allows the data received by one listener

to be limited and assists in flow control over the netlink interface and is

explained in more detail below.

If the exiting task is the last thread exiting its thread group,

an additional record containing the per-tgid stats is also sent to userspace.

The latter contains the sum of per-pid stats for all threads in the thread

group, both past and present.

getdelays.c is a simple utility demonstrating usage of the taskstats interface

for reporting delay accounting statistics.

for reporting delay accounting statistics. Users can register cpumasks,

send commands and process responses, listen for per-tid/tgid exit data,

write the data received to a file and do basic flow control by increasing

receive buffer sizes.

Interface

---------

The taskstats payload is one of the following three kinds:

1. Commands: Sent from user to kernel. The payload is one attribute, of type

TASKSTATS_CMD_ATTR_PID/TGID, containing a u32 pid or tgid in the attribute

payload. The pid/tgid denotes the task/process for which userspace wants

statistics.

1. Commands: Sent from user to kernel. Commands to get data on

a pid/tgid consist of one attribute, of type TASKSTATS_CMD_ATTR_PID/TGID,

containing a u32 pid or tgid in the attribute payload. The pid/tgid denotes

the task/process for which userspace wants statistics.

Commands to register/deregister interest in exit data from a set of cpus

consist of one attribute, of type

TASKSTATS_CMD_ATTR_REGISTER/DEREGISTER_CPUMASK and contain a cpumask in the

attribute payload. The cpumask is specified as an ascii string of

comma-separated cpu ranges e.g. to listen to exit data from cpus 1,2,3,5,7,8

the cpumask would be "1-3,5,7-8". If userspace forgets to deregister interest

in cpus before closing the listening socket, the kernel cleans up its interest

set over time. However, for the sake of efficiency, an explicit deregistration

is advisable.

2. Response for a command: sent from the kernel in response to a userspace

command. The payload is a series of three attributes of type:

unnecessarily receive large structures whose fields are of no interest, then

extending the attributes structure would be worthwhile.

Flow control for taskstats

--------------------------

When the rate of task exits becomes large, a listener may not be able to keep

up with the kernel's rate of sending per-tid/tgid exit data leading to data

loss. This possibility gets compounded when the taskstats structure gets

extended and the number of cpus grows large.

To avoid losing statistics, userspace should do one or more of the following:

- increase the receive buffer sizes for the netlink sockets opened by

listeners to receive exit data.

- create more listeners and reduce the number of cpus being listened to by

each listener. In the extreme case, there could be one listener for each cpu.

Users may also consider setting the cpu affinity of the listener to the subset

of cpus to which it listens, especially if they are listening to just one cpu.

Despite these measures, if the userspace receives ENOBUFS error messages

indicated overflow of receive buffers, it should take measures to handle the

loss of data.

----