[PATCH] per-task-delay-accounting: documentation
Some documentation for delay accounting. Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Signed-off-by: Balbir Singh <balbir@in.ibm.com> Cc: Jes Sorensen <jes@sgi.com> Cc: Peter Chubb <peterc@gelato.unsw.edu.au> Cc: Erich Focht <efocht@ess.nec.de> Cc: Levent Serinol <lserinol@gmail.com> Cc: Jay Lan <jlan@engr.sgi.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
6f44993fe1
commit
a3baf649ca
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@ -0,0 +1,115 @@
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Delay accounting
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----------------
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Tasks encounter delays in execution when they wait
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for some kernel resource to become available e.g. a
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runnable task may wait for a free CPU to run on.
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The per-task delay accounting functionality measures
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the delays experienced by a task while
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a) waiting for a CPU (while being runnable)
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b) completion of synchronous block I/O initiated by the task
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c) swapping in pages
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and makes these statistics available to userspace through
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the taskstats interface.
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Such delays provide feedback for setting a task's cpu priority,
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io priority and rss limit values appropriately. Long delays for
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important tasks could be a trigger for raising its corresponding priority.
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The functionality, through its use of the taskstats interface, also provides
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delay statistics aggregated for all tasks (or threads) belonging to a
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thread group (corresponding to a traditional Unix process). This is a commonly
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needed aggregation that is more efficiently done by the kernel.
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Userspace utilities, particularly resource management applications, can also
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aggregate delay statistics into arbitrary groups. To enable this, delay
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statistics of a task are available both during its lifetime as well as on its
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exit, ensuring continuous and complete monitoring can be done.
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Interface
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---------
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Delay accounting uses the taskstats interface which is described
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in detail in a separate document in this directory. Taskstats returns a
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generic data structure to userspace corresponding to per-pid and per-tgid
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statistics. The delay accounting functionality populates specific fields of
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this structure. See
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include/linux/taskstats.h
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for a description of the fields pertaining to delay accounting.
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It will generally be in the form of counters returning the cumulative
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delay seen for cpu, sync block I/O, swapin etc.
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Taking the difference of two successive readings of a given
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counter (say cpu_delay_total) for a task will give the delay
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experienced by the task waiting for the corresponding resource
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in that interval.
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When a task exits, records containing the per-task and per-process statistics
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are sent to userspace without requiring a command. More details are given in
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the taskstats interface description.
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The getdelays.c userspace utility in this directory allows simple commands to
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be run and the corresponding delay statistics to be displayed. It also serves
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as an example of using the taskstats interface.
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Usage
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-----
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Compile the kernel with
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CONFIG_TASK_DELAY_ACCT=y
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CONFIG_TASKSTATS=y
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Enable the accounting at boot time by adding
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the following to the kernel boot options
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delayacct
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and after the system has booted up, use a utility
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similar to getdelays.c to access the delays
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seen by a given task or a task group (tgid).
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The utility also allows a given command to be
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executed and the corresponding delays to be
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seen.
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General format of the getdelays command
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getdelays [-t tgid] [-p pid] [-c cmd...]
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Get delays, since system boot, for pid 10
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# ./getdelays -p 10
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(output similar to next case)
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Get sum of delays, since system boot, for all pids with tgid 5
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# ./getdelays -t 5
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CPU count real total virtual total delay total
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7876 92005750 100000000 24001500
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IO count delay total
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0 0
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MEM count delay total
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0 0
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Get delays seen in executing a given simple command
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# ./getdelays -c ls /
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bin data1 data3 data5 dev home media opt root srv sys usr
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boot data2 data4 data6 etc lib mnt proc sbin subdomain tmp var
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CPU count real total virtual total delay total
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6 4000250 4000000 0
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IO count delay total
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0 0
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MEM count delay total
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0 0
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@ -0,0 +1,376 @@
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/* getdelays.c
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*
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* Utility to get per-pid and per-tgid delay accounting statistics
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* Also illustrates usage of the taskstats interface
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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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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <unistd.h>
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#include <poll.h>
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#include <string.h>
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#include <fcntl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <signal.h>
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#include <linux/genetlink.h>
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#include <linux/taskstats.h>
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/*
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* Generic macros for dealing with netlink sockets. Might be duplicated
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* elsewhere. It is recommended that commercial grade applications use
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* libnl or libnetlink and use the interfaces provided by the library
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*/
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#define GENLMSG_DATA(glh) ((void *)(NLMSG_DATA(glh) + GENL_HDRLEN))
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#define GENLMSG_PAYLOAD(glh) (NLMSG_PAYLOAD(glh, 0) - GENL_HDRLEN)
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#define NLA_DATA(na) ((void *)((char*)(na) + NLA_HDRLEN))
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#define NLA_PAYLOAD(len) (len - NLA_HDRLEN)
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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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/*
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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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{
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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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fd = socket(AF_NETLINK, SOCK_RAW, protocol);
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if (fd < 0)
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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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{
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struct sockaddr_nl nladdr;
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int r;
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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(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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}
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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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int id;
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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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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 (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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}
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void print_taskstats(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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}
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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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/* 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 {
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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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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 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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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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}
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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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|
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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 */
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printf("error received NACK - leaving\n");
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exit(1);
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}
|
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|
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if (rep_len < 0) {
|
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err(1, "error receiving reply message via Netlink\n");
|
||||
break;
|
||||
}
|
||||
|
||||
/* Validate response message */
|
||||
if (!NLMSG_OK((&ans.n), rep_len))
|
||||
err(1, "invalid reply message received via Netlink\n");
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||||
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||||
rep_len = GENLMSG_PAYLOAD(&ans.n);
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na = (struct nlattr *) GENLMSG_DATA(&ans);
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len = 0;
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i = 0;
|
||||
while (len < rep_len) {
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len += NLA_ALIGN(na->nla_len);
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switch (na->nla_type) {
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case TASKSTATS_TYPE_AGGR_PID:
|
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/* Fall through */
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case TASKSTATS_TYPE_AGGR_TGID:
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aggr_len = NLA_PAYLOAD(na->nla_len);
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len2 = 0;
|
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/* For nested attributes, na follows */
|
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na = (struct nlattr *) NLA_DATA(na);
|
||||
done = 0;
|
||||
while (len2 < aggr_len) {
|
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switch (na->nla_type) {
|
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case TASKSTATS_TYPE_PID:
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rtid = *(int *) NLA_DATA(na);
|
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break;
|
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case TASKSTATS_TYPE_TGID:
|
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rtid = *(int *) NLA_DATA(na);
|
||||
break;
|
||||
case TASKSTATS_TYPE_STATS:
|
||||
if (rtid == tid) {
|
||||
print_taskstats((struct taskstats *)
|
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NLA_DATA(na));
|
||||
done = 1;
|
||||
}
|
||||
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)
|
||||
break;
|
||||
}
|
||||
while (1);
|
||||
|
||||
close(nl_sd);
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -39,6 +39,8 @@ belongs (the task does not need to be the thread group leader). The need for
|
|||
per-tgid stats to be sent for each exiting task is explained in the per-tgid
|
||||
stats section below.
|
||||
|
||||
getdelays.c is a simple utility demonstrating usage of the taskstats interface
|
||||
for reporting delay accounting statistics.
|
||||
|
||||
Interface
|
||||
---------
|
||||
|
|
|
|||
Loading…
Reference in New Issue