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[PATCH] per task delay accounting taskstats interface: documentation fix
Change documentation and example program to reflect the flow control issues being addressed by the cpumask changes. Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Shailabh Nagar
Linus Torvalds
parent
ad4ecbcba7
commit
9e06d3f9f6
@ -5,6 +5,7 @@
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*
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* Copyright (C) Shailabh Nagar, IBM Corp. 2005
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* Copyright (C) Balbir Singh, IBM Corp. 2006
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* Copyright (c) Jay Lan, SGI. 2006
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*
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*/
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@ -36,341 +37,360 @@
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#define err(code, fmt, arg...) do { printf(fmt, ##arg); exit(code); } while (0)
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int done = 0;
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int rcvbufsz=0;
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char name[100];
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int dbg=0, print_delays=0;
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__u64 stime, utime;
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#define PRINTF(fmt, arg...) { \
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if (dbg) { \
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printf(fmt, ##arg); \
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} \
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}
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/* Maximum size of response requested or message sent */
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#define MAX_MSG_SIZE 256
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/* Maximum number of cpus expected to be specified in a cpumask */
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#define MAX_CPUS 32
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/* Maximum length of pathname to log file */
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#define MAX_FILENAME 256
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struct msgtemplate {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[MAX_MSG_SIZE];
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};
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char cpumask[100+6*MAX_CPUS];
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/*
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* Create a raw netlink socket and bind
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*/
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static int create_nl_socket(int protocol, int groups)
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static int create_nl_socket(int protocol)
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{
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socklen_t addr_len;
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int fd;
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struct sockaddr_nl local;
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int fd;
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struct sockaddr_nl local;
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fd = socket(AF_NETLINK, SOCK_RAW, protocol);
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if (fd < 0)
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fd = socket(AF_NETLINK, SOCK_RAW, protocol);
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if (fd < 0)
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return -1;
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if (rcvbufsz)
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if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF,
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&rcvbufsz, sizeof(rcvbufsz)) < 0) {
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printf("Unable to set socket rcv buf size to %d\n",
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rcvbufsz);
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return -1;
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}
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memset(&local, 0, sizeof(local));
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local.nl_family = AF_NETLINK;
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if (bind(fd, (struct sockaddr *) &local, sizeof(local)) < 0)
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goto error;
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return fd;
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error:
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close(fd);
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return -1;
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memset(&local, 0, sizeof(local));
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local.nl_family = AF_NETLINK;
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local.nl_groups = groups;
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if (bind(fd, (struct sockaddr *) &local, sizeof(local)) < 0)
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goto error;
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return fd;
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error:
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close(fd);
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return -1;
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}
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int sendto_fd(int s, const char *buf, int bufLen)
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int send_cmd(int sd, __u16 nlmsg_type, __u32 nlmsg_pid,
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__u8 genl_cmd, __u16 nla_type,
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void *nla_data, int nla_len)
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{
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struct sockaddr_nl nladdr;
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int r;
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struct nlattr *na;
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struct sockaddr_nl nladdr;
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int r, buflen;
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char *buf;
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memset(&nladdr, 0, sizeof(nladdr));
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nladdr.nl_family = AF_NETLINK;
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struct msgtemplate msg;
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while ((r = sendto(s, buf, bufLen, 0, (struct sockaddr *) &nladdr,
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sizeof(nladdr))) < bufLen) {
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if (r > 0) {
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buf += r;
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bufLen -= r;
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} else if (errno != EAGAIN)
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return -1;
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}
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return 0;
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msg.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
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msg.n.nlmsg_type = nlmsg_type;
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msg.n.nlmsg_flags = NLM_F_REQUEST;
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msg.n.nlmsg_seq = 0;
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msg.n.nlmsg_pid = nlmsg_pid;
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msg.g.cmd = genl_cmd;
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msg.g.version = 0x1;
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na = (struct nlattr *) GENLMSG_DATA(&msg);
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na->nla_type = nla_type;
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na->nla_len = nla_len + 1 + NLA_HDRLEN;
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memcpy(NLA_DATA(na), nla_data, nla_len);
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msg.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);
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buf = (char *) &msg;
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buflen = msg.n.nlmsg_len ;
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memset(&nladdr, 0, sizeof(nladdr));
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nladdr.nl_family = AF_NETLINK;
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while ((r = sendto(sd, buf, buflen, 0, (struct sockaddr *) &nladdr,
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sizeof(nladdr))) < buflen) {
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if (r > 0) {
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buf += r;
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buflen -= r;
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} else if (errno != EAGAIN)
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return -1;
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}
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return 0;
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}
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/*
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* Probe the controller in genetlink to find the family id
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* for the TASKSTATS family
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*/
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int get_family_id(int sd)
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{
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struct {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[256];
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} family_req;
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struct {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[256];
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} ans;
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struct {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[256];
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} ans;
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int id;
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struct nlattr *na;
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int rep_len;
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int id, rc;
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struct nlattr *na;
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int rep_len;
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/* Get family name */
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family_req.n.nlmsg_type = GENL_ID_CTRL;
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family_req.n.nlmsg_flags = NLM_F_REQUEST;
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family_req.n.nlmsg_seq = 0;
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family_req.n.nlmsg_pid = getpid();
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family_req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
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family_req.g.cmd = CTRL_CMD_GETFAMILY;
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family_req.g.version = 0x1;
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na = (struct nlattr *) GENLMSG_DATA(&family_req);
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na->nla_type = CTRL_ATTR_FAMILY_NAME;
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na->nla_len = strlen(TASKSTATS_GENL_NAME) + 1 + NLA_HDRLEN;
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strcpy(NLA_DATA(na), TASKSTATS_GENL_NAME);
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family_req.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);
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strcpy(name, TASKSTATS_GENL_NAME);
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rc = send_cmd(sd, GENL_ID_CTRL, getpid(), CTRL_CMD_GETFAMILY,
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CTRL_ATTR_FAMILY_NAME, (void *)name,
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strlen(TASKSTATS_GENL_NAME)+1);
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if (sendto_fd(sd, (char *) &family_req, family_req.n.nlmsg_len) < 0)
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err(1, "error sending message via Netlink\n");
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rep_len = recv(sd, &ans, sizeof(ans), 0);
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if (ans.n.nlmsg_type == NLMSG_ERROR ||
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(rep_len < 0) || !NLMSG_OK((&ans.n), rep_len))
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return 0;
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rep_len = recv(sd, &ans, sizeof(ans), 0);
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if (rep_len < 0)
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err(1, "error receiving reply message via Netlink\n");
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/* Validate response message */
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if (!NLMSG_OK((&ans.n), rep_len))
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err(1, "invalid reply message received via Netlink\n");
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if (ans.n.nlmsg_type == NLMSG_ERROR) { /* error */
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printf("error received NACK - leaving\n");
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exit(1);
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}
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na = (struct nlattr *) GENLMSG_DATA(&ans);
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na = (struct nlattr *) ((char *) na + NLA_ALIGN(na->nla_len));
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if (na->nla_type == CTRL_ATTR_FAMILY_ID) {
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id = *(__u16 *) NLA_DATA(na);
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}
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return id;
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na = (struct nlattr *) GENLMSG_DATA(&ans);
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na = (struct nlattr *) ((char *) na + NLA_ALIGN(na->nla_len));
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if (na->nla_type == CTRL_ATTR_FAMILY_ID) {
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id = *(__u16 *) NLA_DATA(na);
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}
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return id;
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}
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void print_taskstats(struct taskstats *t)
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void print_delayacct(struct taskstats *t)
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{
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printf("\n\nCPU %15s%15s%15s%15s\n"
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" %15llu%15llu%15llu%15llu\n"
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"IO %15s%15s\n"
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" %15llu%15llu\n"
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"MEM %15s%15s\n"
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" %15llu%15llu\n\n",
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"count", "real total", "virtual total", "delay total",
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t->cpu_count, t->cpu_run_real_total, t->cpu_run_virtual_total,
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t->cpu_delay_total,
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"count", "delay total",
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t->blkio_count, t->blkio_delay_total,
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"count", "delay total", t->swapin_count, t->swapin_delay_total);
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}
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void sigchld(int sig)
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{
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done = 1;
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printf("\n\nCPU %15s%15s%15s%15s\n"
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" %15llu%15llu%15llu%15llu\n"
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"IO %15s%15s\n"
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" %15llu%15llu\n"
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"MEM %15s%15s\n"
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" %15llu%15llu\n\n",
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"count", "real total", "virtual total", "delay total",
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t->cpu_count, t->cpu_run_real_total, t->cpu_run_virtual_total,
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t->cpu_delay_total,
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"count", "delay total",
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t->blkio_count, t->blkio_delay_total,
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"count", "delay total", t->swapin_count, t->swapin_delay_total);
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}
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int main(int argc, char *argv[])
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{
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int rc;
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int sk_nl;
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struct nlmsghdr *nlh;
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struct genlmsghdr *genlhdr;
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char *buf;
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struct taskstats_cmd_param *param;
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__u16 id;
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struct nlattr *na;
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int c, rc, rep_len, aggr_len, len2, cmd_type;
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__u16 id;
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__u32 mypid;
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/* For receiving */
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struct sockaddr_nl kern_nla, from_nla;
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socklen_t from_nla_len;
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int recv_len;
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struct taskstats_reply *reply;
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struct nlattr *na;
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int nl_sd = -1;
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int len = 0;
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pid_t tid = 0;
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pid_t rtid = 0;
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struct {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[256];
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} req;
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int fd = 0;
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int count = 0;
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int write_file = 0;
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int maskset = 0;
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char logfile[128];
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int loop = 0;
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struct {
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struct nlmsghdr n;
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struct genlmsghdr g;
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char buf[256];
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} ans;
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struct msgtemplate msg;
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int nl_sd = -1;
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int rep_len;
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int len = 0;
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int aggr_len, len2;
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struct sockaddr_nl nladdr;
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pid_t tid = 0;
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pid_t rtid = 0;
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int cmd_type = TASKSTATS_TYPE_TGID;
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int c, status;
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int forking = 0;
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struct sigaction act = {
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.sa_handler = SIG_IGN,
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.sa_mask = SA_NOMASK,
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};
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struct sigaction tact ;
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while (1) {
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c = getopt(argc, argv, "dw:r:m:t:p:v:l");
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if (c < 0)
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break;
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if (argc < 3) {
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printf("usage %s [-t tgid][-p pid][-c cmd]\n", argv[0]);
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exit(-1);
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}
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tact.sa_handler = sigchld;
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sigemptyset(&tact.sa_mask);
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if (sigaction(SIGCHLD, &tact, NULL) < 0)
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err(1, "sigaction failed for SIGCHLD\n");
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while (1) {
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c = getopt(argc, argv, "t:p:c:");
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if (c < 0)
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break;
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switch (c) {
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case 't':
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tid = atoi(optarg);
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if (!tid)
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err(1, "Invalid tgid\n");
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cmd_type = TASKSTATS_CMD_ATTR_TGID;
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break;
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case 'p':
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tid = atoi(optarg);
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if (!tid)
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err(1, "Invalid pid\n");
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cmd_type = TASKSTATS_CMD_ATTR_TGID;
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break;
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case 'c':
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opterr = 0;
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tid = fork();
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if (tid < 0)
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err(1, "fork failed\n");
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if (tid == 0) { /* child process */
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if (execvp(argv[optind - 1], &argv[optind - 1]) < 0) {
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exit(-1);
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switch (c) {
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case 'd':
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printf("print delayacct stats ON\n");
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print_delays = 1;
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break;
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case 'w':
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strncpy(logfile, optarg, MAX_FILENAME);
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printf("write to file %s\n", logfile);
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write_file = 1;
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break;
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case 'r':
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rcvbufsz = atoi(optarg);
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printf("receive buf size %d\n", rcvbufsz);
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if (rcvbufsz < 0)
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err(1, "Invalid rcv buf size\n");
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break;
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case 'm':
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strncpy(cpumask, optarg, sizeof(cpumask));
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maskset = 1;
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printf("cpumask %s maskset %d\n", cpumask, maskset);
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break;
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case 't':
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tid = atoi(optarg);
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if (!tid)
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err(1, "Invalid tgid\n");
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cmd_type = TASKSTATS_CMD_ATTR_TGID;
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print_delays = 1;
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break;
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case 'p':
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tid = atoi(optarg);
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if (!tid)
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err(1, "Invalid pid\n");
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cmd_type = TASKSTATS_CMD_ATTR_PID;
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print_delays = 1;
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break;
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case 'v':
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printf("debug on\n");
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dbg = 1;
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break;
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case 'l':
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printf("listen forever\n");
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loop = 1;
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break;
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default:
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printf("Unknown option %d\n", c);
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exit(-1);
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}
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}
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forking = 1;
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break;
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default:
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printf("usage %s [-t tgid][-p pid][-c cmd]\n", argv[0]);
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exit(-1);
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break;
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}
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if (c == 'c')
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break;
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}
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/* Construct Netlink request message */
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/* Send Netlink request message & get reply */
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if ((nl_sd =
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create_nl_socket(NETLINK_GENERIC, TASKSTATS_LISTEN_GROUP)) < 0)
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err(1, "error creating Netlink socket\n");
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id = get_family_id(nl_sd);
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/* Send command needed */
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req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
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req.n.nlmsg_type = id;
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req.n.nlmsg_flags = NLM_F_REQUEST;
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req.n.nlmsg_seq = 0;
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req.n.nlmsg_pid = tid;
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req.g.cmd = TASKSTATS_CMD_GET;
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na = (struct nlattr *) GENLMSG_DATA(&req);
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na->nla_type = cmd_type;
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na->nla_len = sizeof(unsigned int) + NLA_HDRLEN;
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*(__u32 *) NLA_DATA(na) = tid;
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req.n.nlmsg_len += NLMSG_ALIGN(na->nla_len);
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if (!forking && sendto_fd(nl_sd, (char *) &req, req.n.nlmsg_len) < 0)
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err(1, "error sending message via Netlink\n");
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act.sa_handler = SIG_IGN;
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sigemptyset(&act.sa_mask);
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if (sigaction(SIGINT, &act, NULL) < 0)
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err(1, "sigaction failed for SIGINT\n");
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do {
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int i;
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struct pollfd pfd;
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int pollres;
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pfd.events = 0xffff & ~POLLOUT;
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pfd.fd = nl_sd;
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pollres = poll(&pfd, 1, 5000);
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if (pollres < 0 || done) {
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break;
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}
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rep_len = recv(nl_sd, &ans, sizeof(ans), 0);
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nladdr.nl_family = AF_NETLINK;
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nladdr.nl_groups = TASKSTATS_LISTEN_GROUP;
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if (ans.n.nlmsg_type == NLMSG_ERROR) { /* error */
|
||||
printf("error received NACK - leaving\n");
|
||||
exit(1);
|
||||
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 (rep_len < 0) {
|
||||
err(1, "error receiving reply message via Netlink\n");
|
||||
break;
|
||||
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;
|
||||
}
|
||||
}
|
||||
|
||||
/* Validate response message */
|
||||
if (!NLMSG_OK((&ans.n), rep_len))
|
||||
err(1, "invalid reply message received via Netlink\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;
|
||||
}
|
||||
}
|
||||
|
||||
rep_len = GENLMSG_PAYLOAD(&ans.n);
|
||||
do {
|
||||
int i;
|
||||
|
||||
na = (struct nlattr *) GENLMSG_DATA(&ans);
|
||||
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:
|
||||
aggr_len = NLA_PAYLOAD(na->nla_len);
|
||||
len2 = 0;
|
||||
/* For nested attributes, na follows */
|
||||
na = (struct nlattr *) NLA_DATA(na);
|
||||
done = 0;
|
||||
while (len2 < aggr_len) {
|
||||
switch (na->nla_type) {
|
||||
case TASKSTATS_TYPE_PID:
|
||||
rtid = *(int *) NLA_DATA(na);
|
||||
break;
|
||||
case TASKSTATS_TYPE_TGID:
|
||||
rtid = *(int *) NLA_DATA(na);
|
||||
break;
|
||||
case TASKSTATS_TYPE_STATS:
|
||||
if (rtid == tid) {
|
||||
print_taskstats((struct taskstats *)
|
||||
NLA_DATA(na));
|
||||
done = 1;
|
||||
rep_len = recv(nl_sd, &msg, sizeof(msg), 0);
|
||||
PRINTF("received %d bytes\n", rep_len);
|
||||
|
||||
if (rep_len < 0) {
|
||||
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;
|
||||
}
|
||||
|
||||
PRINTF("nlmsghdr size=%d, nlmsg_len=%d, rep_len=%d\n",
|
||||
sizeof(struct nlmsghdr), msg.n.nlmsg_len, rep_len);
|
||||
|
||||
|
||||
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_TGID:
|
||||
/* Fall through */
|
||||
case TASKSTATS_TYPE_AGGR_PID:
|
||||
aggr_len = NLA_PAYLOAD(na->nla_len);
|
||||
len2 = 0;
|
||||
/* For nested attributes, na follows */
|
||||
na = (struct nlattr *) NLA_DATA(na);
|
||||
done = 0;
|
||||
while (len2 < aggr_len) {
|
||||
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:
|
||||
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);
|
||||
}
|
||||
break;
|
||||
|
||||
default:
|
||||
printf("Unknown nla_type %d\n", na->nla_type);
|
||||
break;
|
||||
}
|
||||
break;
|
||||
}
|
||||
len2 += NLA_ALIGN(na->nla_len);
|
||||
na = (struct nlattr *) ((char *) na + len2);
|
||||
if (done)
|
||||
break;
|
||||
na = (struct nlattr *) (GENLMSG_DATA(&msg) + len);
|
||||
}
|
||||
}
|
||||
na = (struct nlattr *) (GENLMSG_DATA(&ans) + len);
|
||||
if (done)
|
||||
break;
|
||||
} 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");
|
||||
}
|
||||
if (done)
|
||||
break;
|
||||
}
|
||||
while (1);
|
||||
|
||||
close(nl_sd);
|
||||
return 0;
|
||||
err:
|
||||
close(nl_sd);
|
||||
if (fd)
|
||||
close(fd);
|
||||
return 0;
|
||||
}
|
||||
|
||||
@ -26,20 +26,28 @@ leader - a process is deemed alive as long as it has any task belonging to it.
|
||||
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
|
||||
---------
|
||||
@ -66,10 +74,20 @@ The messages are in the format
|
||||
|
||||
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:
|
||||
@ -138,4 +156,26 @@ struct too much, requiring disparate userspace accounting utilities to
|
||||
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.
|
||||
|
||||
----
|
||||
|
||||
Loading…
Reference in New Issue
Block a user