--- /dev/null
+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 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, two records are sent by the kernel to
+each listener on the multicast socket. The first the per-pid task's statistics
+and the second is the sum for all tasks of the process to which the task
+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.
+
+
+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. 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.
+
+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. Hence the taskstats implementation
+dynamically sums up the per-task stats for each task belonging to a process
+whenever per-process stats are needed.
+
+Not maintaining per-tgid stats creates a problem when userspace is interested
+in getting these stats when the process dies i.e. the last thread of
+a process exits. It isn't possible to simply return some aggregated per-process
+statistic from the kernel.
+
+The approach taken by taskstats is to return the per-tgid stats *each* time
+a task exits, in addition to the per-pid stats for that task. Userspace can
+maintain task<->process mappings and use them to maintain the per-process stats
+in userspace, updating the aggregate appropriately as the tasks of a process
+exit.
+
+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.
+
+----
--- /dev/null
+/* taskstats.h - exporting per-task statistics
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ * (C) Balbir Singh, IBM Corp. 2006
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+#ifndef _LINUX_TASKSTATS_H
+#define _LINUX_TASKSTATS_H
+
+/* Format for per-task data returned to userland when
+ * - a task exits
+ * - listener requests stats for a task
+ *
+ * The struct is versioned. Newer versions should only add fields to
+ * the bottom of the struct to maintain backward compatibility.
+ *
+ *
+ * To add new fields
+ * a) bump up TASKSTATS_VERSION
+ * b) add comment indicating new version number at end of struct
+ * c) add new fields after version comment; maintain 64-bit alignment
+ */
+
+#define TASKSTATS_VERSION 1
+
+struct taskstats {
+
+ /* Version 1 */
+ __u64 version;
+};
+
+
+#define TASKSTATS_LISTEN_GROUP 0x1
+
+/*
+ * Commands sent from userspace
+ * Not versioned. New commands should only be inserted at the enum's end
+ * prior to __TASKSTATS_CMD_MAX
+ */
+
+enum {
+ TASKSTATS_CMD_UNSPEC = 0, /* Reserved */
+ TASKSTATS_CMD_GET, /* user->kernel request/get-response */
+ TASKSTATS_CMD_NEW, /* kernel->user event */
+ __TASKSTATS_CMD_MAX,
+};
+
+#define TASKSTATS_CMD_MAX (__TASKSTATS_CMD_MAX - 1)
+
+enum {
+ TASKSTATS_TYPE_UNSPEC = 0, /* Reserved */
+ TASKSTATS_TYPE_PID, /* Process id */
+ TASKSTATS_TYPE_TGID, /* Thread group id */
+ TASKSTATS_TYPE_STATS, /* taskstats structure */
+ TASKSTATS_TYPE_AGGR_PID, /* contains pid + stats */
+ TASKSTATS_TYPE_AGGR_TGID, /* contains tgid + stats */
+ __TASKSTATS_TYPE_MAX,
+};
+
+#define TASKSTATS_TYPE_MAX (__TASKSTATS_TYPE_MAX - 1)
+
+enum {
+ TASKSTATS_CMD_ATTR_UNSPEC = 0,
+ TASKSTATS_CMD_ATTR_PID,
+ TASKSTATS_CMD_ATTR_TGID,
+ __TASKSTATS_CMD_ATTR_MAX,
+};
+
+#define TASKSTATS_CMD_ATTR_MAX (__TASKSTATS_CMD_ATTR_MAX - 1)
+
+/* NETLINK_GENERIC related info */
+
+#define TASKSTATS_GENL_NAME "TASKSTATS"
+#define TASKSTATS_GENL_VERSION 0x1
+
+#endif /* _LINUX_TASKSTATS_H */
--- /dev/null
+/* taskstats_kern.h - kernel header for per-task statistics interface
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ * (C) Balbir Singh, IBM Corp. 2006
+ */
+
+#ifndef _LINUX_TASKSTATS_KERN_H
+#define _LINUX_TASKSTATS_KERN_H
+
+#include <linux/taskstats.h>
+#include <linux/sched.h>
+
+enum {
+ TASKSTATS_MSG_UNICAST, /* send data only to requester */
+ TASKSTATS_MSG_MULTICAST, /* send data to a group */
+};
+
+#ifdef CONFIG_TASKSTATS
+extern kmem_cache_t *taskstats_cache;
+
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
+ struct taskstats **ptgidstats)
+{
+ *ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+ *ptgidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+}
+
+static inline void taskstats_exit_free(struct taskstats *tidstats,
+ struct taskstats *tgidstats)
+{
+ if (tidstats)
+ kmem_cache_free(taskstats_cache, tidstats);
+ if (tgidstats)
+ kmem_cache_free(taskstats_cache, tgidstats);
+}
+
+extern void taskstats_exit_send(struct task_struct *, struct taskstats *,
+ struct taskstats *);
+extern void taskstats_init_early(void);
+
+#else
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
+ struct taskstats **ptgidstats)
+{}
+static inline void taskstats_exit_free(struct taskstats *ptidstats,
+ struct taskstats *ptgidstats)
+{}
+static inline void taskstats_exit_send(struct task_struct *tsk,
+ struct taskstats *tidstats,
+ struct taskstats *tgidstats)
+{}
+static inline void taskstats_init_early(void)
+{}
+#endif /* CONFIG_TASKSTATS */
+
+#endif
+
for processing it. A preliminary version of these tools is available
at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
+config TASKSTATS
+ bool "Export task/process statistics through netlink (EXPERIMENTAL)"
+ depends on NET
+ default n
+ help
+ Export selected statistics for tasks/processes through the
+ generic netlink interface. Unlike BSD process accounting, the
+ statistics are available during the lifetime of tasks/processes as
+ responses to commands. Like BSD accounting, they are sent to user
+ space on task exit.
+
+ Say N if unsure.
+
config TASK_DELAY_ACCT
bool "Enable per-task delay accounting (EXPERIMENTAL)"
help
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/efi.h>
+#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/unistd.h>
#include <linux/rmap.h>
proc_root_init();
#endif
cpuset_init();
+ taskstats_init_early();
delayacct_init();
check_bugs();
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
+obj-$(CONFIG_TASKSTATS) += taskstats.o
ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
#include <linux/mount.h>
#include <linux/proc_fs.h>
#include <linux/mempolicy.h>
+#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/cpuset.h>
#include <linux/syscalls.h>
fastcall NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
+ struct taskstats *tidstats, *tgidstats;
int group_dead;
profile_task_exit(tsk);
current->comm, current->pid,
preempt_count());
+ taskstats_exit_alloc(&tidstats, &tgidstats);
+
acct_update_integrals(tsk);
if (tsk->mm) {
update_hiwater_rss(tsk->mm);
#endif
if (unlikely(tsk->audit_context))
audit_free(tsk);
+ taskstats_exit_send(tsk, tidstats, tgidstats);
+ taskstats_exit_free(tidstats, tgidstats);
delayacct_tsk_exit(tsk);
+
exit_mm(tsk);
if (group_dead)
--- /dev/null
+/*
+ * taskstats.c - Export per-task statistics to userland
+ *
+ * Copyright (C) Shailabh Nagar, IBM Corp. 2006
+ * (C) Balbir Singh, IBM Corp. 2006
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/taskstats_kern.h>
+#include <net/genetlink.h>
+#include <asm/atomic.h>
+
+static DEFINE_PER_CPU(__u32, taskstats_seqnum) = { 0 };
+static int family_registered;
+kmem_cache_t *taskstats_cache;
+static DEFINE_MUTEX(taskstats_exit_mutex);
+
+static struct genl_family family = {
+ .id = GENL_ID_GENERATE,
+ .name = TASKSTATS_GENL_NAME,
+ .version = TASKSTATS_GENL_VERSION,
+ .maxattr = TASKSTATS_CMD_ATTR_MAX,
+};
+
+static struct nla_policy taskstats_cmd_get_policy[TASKSTATS_CMD_ATTR_MAX+1]
+__read_mostly = {
+ [TASKSTATS_CMD_ATTR_PID] = { .type = NLA_U32 },
+ [TASKSTATS_CMD_ATTR_TGID] = { .type = NLA_U32 },
+};
+
+
+static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
+ void **replyp, size_t size)
+{
+ struct sk_buff *skb;
+ void *reply;
+
+ /*
+ * If new attributes are added, please revisit this allocation
+ */
+ skb = nlmsg_new(size);
+ if (!skb)
+ return -ENOMEM;
+
+ if (!info) {
+ int seq = get_cpu_var(taskstats_seqnum)++;
+ put_cpu_var(taskstats_seqnum);
+
+ reply = genlmsg_put(skb, 0, seq,
+ family.id, 0, 0,
+ cmd, family.version);
+ } else
+ reply = genlmsg_put(skb, info->snd_pid, info->snd_seq,
+ family.id, 0, 0,
+ cmd, family.version);
+ if (reply == NULL) {
+ nlmsg_free(skb);
+ return -EINVAL;
+ }
+
+ *skbp = skb;
+ *replyp = reply;
+ return 0;
+}
+
+static int send_reply(struct sk_buff *skb, pid_t pid, int event)
+{
+ struct genlmsghdr *genlhdr = nlmsg_data((struct nlmsghdr *)skb->data);
+ void *reply;
+ int rc;
+
+ reply = genlmsg_data(genlhdr);
+
+ rc = genlmsg_end(skb, reply);
+ if (rc < 0) {
+ nlmsg_free(skb);
+ return rc;
+ }
+
+ if (event == TASKSTATS_MSG_MULTICAST)
+ return genlmsg_multicast(skb, pid, TASKSTATS_LISTEN_GROUP);
+ return genlmsg_unicast(skb, pid);
+}
+
+static int fill_pid(pid_t pid, struct task_struct *pidtsk,
+ struct taskstats *stats)
+{
+ int rc;
+ struct task_struct *tsk = pidtsk;
+
+ if (!pidtsk) {
+ read_lock(&tasklist_lock);
+ tsk = find_task_by_pid(pid);
+ if (!tsk) {
+ read_unlock(&tasklist_lock);
+ return -ESRCH;
+ }
+ get_task_struct(tsk);
+ read_unlock(&tasklist_lock);
+ } else
+ get_task_struct(tsk);
+
+ /*
+ * Each accounting subsystem adds calls to its functions to
+ * fill in relevant parts of struct taskstsats as follows
+ *
+ * rc = per-task-foo(stats, tsk);
+ * if (rc)
+ * goto err;
+ */
+
+err:
+ put_task_struct(tsk);
+ return rc;
+
+}
+
+static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
+ struct taskstats *stats)
+{
+ int rc;
+ struct task_struct *tsk, *first;
+
+ first = tgidtsk;
+ read_lock(&tasklist_lock);
+ if (!first) {
+ first = find_task_by_pid(tgid);
+ if (!first) {
+ read_unlock(&tasklist_lock);
+ return -ESRCH;
+ }
+ }
+ tsk = first;
+ do {
+ /*
+ * Each accounting subsystem adds calls its functions to
+ * fill in relevant parts of struct taskstsats as follows
+ *
+ * rc = per-task-foo(stats, tsk);
+ * if (rc)
+ * break;
+ */
+
+ } while_each_thread(first, tsk);
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Accounting subsytems can also add calls here if they don't
+ * wish to aggregate statistics for per-tgid stats
+ */
+
+ return rc;
+}
+
+static int taskstats_send_stats(struct sk_buff *skb, struct genl_info *info)
+{
+ int rc = 0;
+ struct sk_buff *rep_skb;
+ struct taskstats stats;
+ void *reply;
+ size_t size;
+ struct nlattr *na;
+
+ /*
+ * Size includes space for nested attributes
+ */
+ size = nla_total_size(sizeof(u32)) +
+ nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+
+ memset(&stats, 0, sizeof(stats));
+ rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+ if (rc < 0)
+ return rc;
+
+ if (info->attrs[TASKSTATS_CMD_ATTR_PID]) {
+ u32 pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
+ rc = fill_pid(pid, NULL, &stats);
+ if (rc < 0)
+ goto err;
+
+ na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_PID);
+ NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_PID, pid);
+ NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+ stats);
+ } else if (info->attrs[TASKSTATS_CMD_ATTR_TGID]) {
+ u32 tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
+ rc = fill_tgid(tgid, NULL, &stats);
+ if (rc < 0)
+ goto err;
+
+ na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_TGID);
+ NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_TGID, tgid);
+ NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+ stats);
+ } else {
+ rc = -EINVAL;
+ goto err;
+ }
+
+ nla_nest_end(rep_skb, na);
+
+ return send_reply(rep_skb, info->snd_pid, TASKSTATS_MSG_UNICAST);
+
+nla_put_failure:
+ return genlmsg_cancel(rep_skb, reply);
+err:
+ nlmsg_free(rep_skb);
+ return rc;
+}
+
+/* Send pid data out on exit */
+void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
+ struct taskstats *tgidstats)
+{
+ int rc;
+ struct sk_buff *rep_skb;
+ void *reply;
+ size_t size;
+ int is_thread_group;
+ struct nlattr *na;
+
+ if (!family_registered || !tidstats)
+ return;
+
+ mutex_lock(&taskstats_exit_mutex);
+
+ is_thread_group = !thread_group_empty(tsk);
+ rc = 0;
+
+ /*
+ * Size includes space for nested attributes
+ */
+ size = nla_total_size(sizeof(u32)) +
+ nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
+
+ if (is_thread_group)
+ size = 2 * size; /* PID + STATS + TGID + STATS */
+
+ rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, &reply, size);
+ if (rc < 0)
+ goto ret;
+
+ rc = fill_pid(tsk->pid, tsk, tidstats);
+ if (rc < 0)
+ goto err_skb;
+
+ na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_PID);
+ NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_PID, (u32)tsk->pid);
+ NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+ *tidstats);
+ nla_nest_end(rep_skb, na);
+
+ if (!is_thread_group || !tgidstats) {
+ send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+ goto ret;
+ }
+
+ rc = fill_tgid(tsk->pid, tsk, tgidstats);
+ /*
+ * If fill_tgid() failed then one probable reason could be that the
+ * thread group leader has exited. fill_tgid() will fail, send out
+ * the pid statistics collected earlier.
+ */
+ if (rc < 0) {
+ send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+ goto ret;
+ }
+
+ na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_TGID);
+ NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_TGID, (u32)tsk->tgid);
+ NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
+ *tgidstats);
+ nla_nest_end(rep_skb, na);
+
+ send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
+ goto ret;
+
+nla_put_failure:
+ genlmsg_cancel(rep_skb, reply);
+ goto ret;
+err_skb:
+ nlmsg_free(rep_skb);
+ret:
+ mutex_unlock(&taskstats_exit_mutex);
+ return;
+}
+
+static struct genl_ops taskstats_ops = {
+ .cmd = TASKSTATS_CMD_GET,
+ .doit = taskstats_send_stats,
+ .policy = taskstats_cmd_get_policy,
+};
+
+/* Needed early in initialization */
+void __init taskstats_init_early(void)
+{
+ taskstats_cache = kmem_cache_create("taskstats_cache",
+ sizeof(struct taskstats),
+ 0, SLAB_PANIC, NULL, NULL);
+}
+
+static int __init taskstats_init(void)
+{
+ int rc;
+
+ rc = genl_register_family(&family);
+ if (rc)
+ return rc;
+
+ rc = genl_register_ops(&family, &taskstats_ops);
+ if (rc < 0)
+ goto err;
+
+ family_registered = 1;
+ return 0;
+err:
+ genl_unregister_family(&family);
+ return rc;
+}
+
+/*
+ * late initcall ensures initialization of statistics collection
+ * mechanisms precedes initialization of the taskstats interface
+ */
+late_initcall(taskstats_init);
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff