diff options
Diffstat (limited to 'Documentation/accounting')
| -rw-r--r-- | Documentation/accounting/delay-accounting.txt | 110 | ||||
| -rw-r--r-- | Documentation/accounting/getdelays.c | 396 | ||||
| -rw-r--r-- | Documentation/accounting/taskstats.txt | 181 |
3 files changed, 687 insertions, 0 deletions
diff --git a/Documentation/accounting/delay-accounting.txt b/Documentation/accounting/delay-accounting.txt new file mode 100644 index 00000000000..be215e58423 --- /dev/null +++ b/Documentation/accounting/delay-accounting.txt @@ -0,0 +1,110 @@ +Delay accounting +---------------- + +Tasks encounter delays in execution when they wait +for some kernel resource to become available e.g. a +runnable task may wait for a free CPU to run on. + +The per-task delay accounting functionality measures +the delays experienced by a task while + +a) waiting for a CPU (while being runnable) +b) completion of synchronous block I/O initiated by the task +c) swapping in pages + +and makes these statistics available to userspace through +the taskstats interface. + +Such delays provide feedback for setting a task's cpu priority, +io priority and rss limit values appropriately. Long delays for +important tasks could be a trigger for raising its corresponding priority. + +The functionality, through its use of the taskstats interface, also provides +delay statistics aggregated for all tasks (or threads) belonging to a +thread group (corresponding to a traditional Unix process). This is a commonly +needed aggregation that is more efficiently done by the kernel. + +Userspace utilities, particularly resource management applications, can also +aggregate delay statistics into arbitrary groups. To enable this, delay +statistics of a task are available both during its lifetime as well as on its +exit, ensuring continuous and complete monitoring can be done. + + +Interface +--------- + +Delay accounting uses the taskstats interface which is described +in detail in a separate document in this directory. Taskstats returns a +generic data structure to userspace corresponding to per-pid and per-tgid +statistics. The delay accounting functionality populates specific fields of +this structure. See + include/linux/taskstats.h +for a description of the fields pertaining to delay accounting. +It will generally be in the form of counters returning the cumulative +delay seen for cpu, sync block I/O, swapin etc. + +Taking the difference of two successive readings of a given +counter (say cpu_delay_total) for a task will give the delay +experienced by the task waiting for the corresponding resource +in that interval. + +When a task exits, records containing the per-task statistics +are sent to userspace without requiring a command. If it is the last exiting +task of a thread group, the per-tgid statistics are also sent. More details +are given in the taskstats interface description. + +The getdelays.c userspace utility in this directory allows simple commands to +be run and the corresponding delay statistics to be displayed. It also serves +as an example of using the taskstats interface. + +Usage +----- + +Compile the kernel with + CONFIG_TASK_DELAY_ACCT=y + CONFIG_TASKSTATS=y + +Enable the accounting at boot time by adding +the following to the kernel boot options + delayacct + +and after the system has booted up, use a utility +similar to getdelays.c to access the delays +seen by a given task or a task group (tgid). +The utility also allows a given command to be +executed and the corresponding delays to be +seen. + +General format of the getdelays command + +getdelays [-t tgid] [-p pid] [-c cmd...] + + +Get delays, since system boot, for pid 10 +# ./getdelays -p 10 +(output similar to next case) + +Get sum of delays, since system boot, for all pids with tgid 5 +# ./getdelays -t 5 + + +CPU count real total virtual total delay total + 7876 92005750 100000000 24001500 +IO count delay total + 0 0 +MEM count delay total + 0 0 + +Get delays seen in executing a given simple command +# ./getdelays -c ls / + +bin data1 data3 data5 dev home media opt root srv sys usr +boot data2 data4 data6 etc lib mnt proc sbin subdomain tmp var + + +CPU count real total virtual total delay total + 6 4000250 4000000 0 +IO count delay total + 0 0 +MEM count delay total + 0 0 diff --git a/Documentation/accounting/getdelays.c b/Documentation/accounting/getdelays.c new file mode 100644 index 00000000000..795ca3911cc --- /dev/null +++ b/Documentation/accounting/getdelays.c @@ -0,0 +1,396 @@ +/* getdelays.c + * + * Utility to get per-pid and per-tgid delay accounting statistics + * Also illustrates usage of the taskstats interface + * + * Copyright (C) Shailabh Nagar, IBM Corp. 2005 + * Copyright (C) Balbir Singh, IBM Corp. 2006 + * Copyright (c) Jay Lan, SGI. 2006 + * + */ + +#include <stdio.h> +#include <stdlib.h> +#include <errno.h> +#include <unistd.h> +#include <poll.h> +#include <string.h> +#include <fcntl.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/socket.h> +#include <sys/types.h> +#include <signal.h> + +#include <linux/genetlink.h> +#include <linux/taskstats.h> + +/* + * Generic macros for dealing with netlink sockets. Might be duplicated + * elsewhere. It is recommended that commercial grade applications use + * libnl or libnetlink and use the interfaces provided by the library + */ +#define GENLMSG_DATA(glh) ((void *)(NLMSG_DATA(glh) + GENL_HDRLEN)) +#define GENLMSG_PAYLOAD(glh) (NLMSG_PAYLOAD(glh, 0) - GENL_HDRLEN) +#define NLA_DATA(na) ((void *)((char*)(na) + NLA_HDRLEN)) +#define NLA_PAYLOAD(len) (len - NLA_HDRLEN) + +#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 fd; + struct sockaddr_nl local; + + fd = socket(AF_NETLINK, SOCK_RAW, protocol); + 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; + + if (bind(fd, (struct sockaddr *) &local, sizeof(local)) < 0) + goto error; + + return fd; +error: + close(fd); + return -1; +} + + +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, 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(sd, buf, buflen, 0, (struct sockaddr *) &nladdr, + sizeof(nladdr))) < buflen) { + if (r > 0) { + buf += 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]; + } ans; + + int id, rc; + struct nlattr *na; + int rep_len; + + 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 (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)); + if (na->nla_type == CTRL_ATTR_FAMILY_ID) { + id = *(__u16 *) NLA_DATA(na); + } + return id; +} + +void print_delayacct(struct taskstats *t) +{ + printf("\n\nCPU %15s%15s%15s%15s\n" + " %15llu%15llu%15llu%15llu\n" + "IO %15s%15s\n" + " %15llu%15llu\n" + "MEM %15s%15s\n" + " %15llu%15llu\n\n", + "count", "real total", "virtual total", "delay total", + t->cpu_count, t->cpu_run_real_total, t->cpu_run_virtual_total, + t->cpu_delay_total, + "count", "delay total", + t->blkio_count, t->blkio_delay_total, + "count", "delay total", t->swapin_count, t->swapin_delay_total); +} + +int main(int argc, char *argv[]) +{ + int c, rc, rep_len, aggr_len, len2, cmd_type; + __u16 id; + __u32 mypid; + + struct nlattr *na; + int nl_sd = -1; + int len = 0; + pid_t tid = 0; + pid_t rtid = 0; + + int fd = 0; + int count = 0; + int write_file = 0; + int maskset = 0; + char logfile[128]; + int loop = 0; + + struct msgtemplate msg; + + while (1) { + 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_PID; + print_delays = 1; + break; + case 'v': + printf("debug on\n"); + dbg = 1; + break; + case 'l': + printf("listen forever\n"); + loop = 1; + break; + default: + printf("Unknown option %d\n", c); + 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 ((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; + } + } + + 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; + + 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; + } + 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; +} diff --git a/Documentation/accounting/taskstats.txt b/Documentation/accounting/taskstats.txt new file mode 100644 index 00000000000..92ebf29e904 --- /dev/null +++ b/Documentation/accounting/taskstats.txt @@ -0,0 +1,181 @@ +Per-task statistics interface +----------------------------- + + +Taskstats is a netlink-based interface for sending per-task and +per-process statistics from the kernel to userspace. + +Taskstats was designed for the following benefits: + +- efficiently provide statistics during lifetime of a task and on its exit +- unified interface for multiple accounting subsystems +- extensibility for use by future accounting patches + +Terminology +----------- + +"pid", "tid" and "task" are used interchangeably and refer to the standard +Linux task defined by struct task_struct. per-pid stats are the same as +per-task stats. + +"tgid", "process" and "thread group" are used interchangeably and refer to the +tasks that share an mm_struct i.e. the traditional Unix process. Despite the +use of tgid, there is no special treatment for the task that is thread group +leader - a process is deemed alive as long as it has any task belonging to it. + +Usage +----- + +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, 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. 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 user-kernel interface is encapsulated in include/linux/taskstats.h + +To avoid this documentation becoming obsolete as the interface evolves, only +an outline of the current version is given. taskstats.h always overrides the +description here. + +struct taskstats is the common accounting structure for both per-pid and +per-tgid data. It is versioned and can be extended by each accounting subsystem +that is added to the kernel. The fields and their semantics are defined in the +taskstats.h file. + +The data exchanged between user and kernel space is a netlink message belonging +to the NETLINK_GENERIC family and using the netlink attributes interface. +The messages are in the format + + +----------+- - -+-------------+-------------------+ + | nlmsghdr | Pad | genlmsghdr | taskstats payload | + +----------+- - -+-------------+-------------------+ + + +The taskstats payload is one of the following three kinds: + +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: + +a) TASKSTATS_TYPE_AGGR_PID/TGID : attribute containing no payload but indicates +a pid/tgid will be followed by some stats. + +b) TASKSTATS_TYPE_PID/TGID: attribute whose payload is the pid/tgid whose stats +is being returned. + +c) TASKSTATS_TYPE_STATS: attribute with a struct taskstsats as payload. The +same structure is used for both per-pid and per-tgid stats. + +3. New message sent by kernel whenever a task exits. The payload consists of a + series of attributes of the following type: + +a) TASKSTATS_TYPE_AGGR_PID: indicates next two attributes will be pid+stats +b) TASKSTATS_TYPE_PID: contains exiting task's pid +c) TASKSTATS_TYPE_STATS: contains the exiting task's per-pid stats +d) TASKSTATS_TYPE_AGGR_TGID: indicates next two attributes will be tgid+stats +e) TASKSTATS_TYPE_TGID: contains tgid of process to which task belongs +f) TASKSTATS_TYPE_STATS: contains the per-tgid stats for exiting task's process + + +per-tgid stats +-------------- + +Taskstats provides per-process stats, in addition to per-task stats, since +resource management is often done at a process granularity and aggregating task +stats in userspace alone is inefficient and potentially inaccurate (due to lack +of atomicity). + +However, maintaining per-process, in addition to per-task stats, within the +kernel has space and time overheads. To address this, the taskstats code +accumalates each exiting task's statistics into a process-wide data structure. +When the last task of a process exits, the process level data accumalated also +gets sent to userspace (along with the per-task data). + +When a user queries to get per-tgid data, the sum of all other live threads in +the group is added up and added to the accumalated total for previously exited +threads of the same thread group. + +Extending taskstats +------------------- + +There are two ways to extend the taskstats interface to export more +per-task/process stats as patches to collect them get added to the kernel +in future: + +1. Adding more fields to the end of the existing struct taskstats. Backward + compatibility is ensured by the version number within the + structure. Userspace will use only the fields of the struct that correspond + to the version its using. + +2. Defining separate statistic structs and using the netlink attributes + interface to return them. Since userspace processes each netlink attribute + independently, it can always ignore attributes whose type it does not + understand (because it is using an older version of the interface). + + +Choosing between 1. and 2. is a matter of trading off flexibility and +overhead. If only a few fields need to be added, then 1. is the preferable +path since the kernel and userspace don't need to incur the overhead of +processing new netlink attributes. But if the new fields expand the existing +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. + +---- |