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authorShailabh Nagar <nagar@watson.ibm.com>2006-07-14 00:24:44 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-07-14 21:53:57 -0700
commitad4ecbcba72855a2b5319b96e2a3a65ed1ca3bfd (patch)
treea2f5b98598948525de77ab594e4432f09a230388
parent25890454667b3295f67b3372352be90705f8667c (diff)
downloadlinaro-lsk-ad4ecbcba72855a2b5319b96e2a3a65ed1ca3bfd.tar.gz
[PATCH] delay accounting taskstats interface send tgid once
Send per-tgid data only once during exit of a thread group instead of once with each member thread exit. Currently, when a thread exits, besides its per-tid data, the per-tgid data of its thread group is also sent out, if its thread group is non-empty. The per-tgid data sent consists of the sum of per-tid stats for all *remaining* threads of the thread group. This patch modifies this sending in two ways: - the per-tgid data is sent only when the last thread of a thread group exits. This cuts down heavily on the overhead of sending/receiving per-tgid data, especially when other exploiters of the taskstats interface aren't interested in per-tgid stats - the semantics of the per-tgid data sent are changed. Instead of being the sum of per-tid data for remaining threads, the value now sent is the true total accumalated statistics for all threads that are/were part of the thread group. The patch also addresses a minor issue where failure of one accounting subsystem to fill in the taskstats structure was causing the send of taskstats to not be sent at all. The patch has been tested for stability and run cerberus for over 4 hours on an SMP. [akpm@osdl.org: bugfixes] Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Signed-off-by: Balbir Singh <balbir@in.ibm.com> Cc: Jay Lan <jlan@engr.sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--Documentation/accounting/delay-accounting.txt13
-rw-r--r--Documentation/accounting/taskstats.txt33
-rw-r--r--MAINTAINERS12
-rw-r--r--include/linux/sched.h4
-rw-r--r--include/linux/taskstats_kern.h71
-rw-r--r--kernel/exit.c8
-rw-r--r--kernel/fork.c4
-rw-r--r--kernel/taskstats.c98
8 files changed, 162 insertions, 81 deletions
diff --git a/Documentation/accounting/delay-accounting.txt b/Documentation/accounting/delay-accounting.txt
index f3dc0ca04fa..be215e58423 100644
--- a/Documentation/accounting/delay-accounting.txt
+++ b/Documentation/accounting/delay-accounting.txt
@@ -48,9 +48,10 @@ 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 and per-process statistics
-are sent to userspace without requiring a command. More details are given in
-the taskstats interface description.
+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
@@ -107,9 +108,3 @@ IO count delay total
0 0
MEM count delay total
0 0
-
-
-
-
-
-
diff --git a/Documentation/accounting/taskstats.txt b/Documentation/accounting/taskstats.txt
index acc6b4f37fc..efd8f605bcd 100644
--- a/Documentation/accounting/taskstats.txt
+++ b/Documentation/accounting/taskstats.txt
@@ -32,12 +32,11 @@ 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.
+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.
getdelays.c is a simple utility demonstrating usage of the taskstats interface
for reporting delay accounting statistics.
@@ -104,20 +103,14 @@ 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.
+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
-------------------
diff --git a/MAINTAINERS b/MAINTAINERS
index 0557cfde053..e99028ca2f7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2240,6 +2240,12 @@ M: tsbogend@alpha.franken.de
L: netdev@vger.kernel.org
S: Maintained
+PER-TASK DELAY ACCOUNTING
+P: Shailabh Nagar
+M: nagar@watson.ibm.com
+L: linux-kernel@vger.kernel.org
+S: Maintained
+
PERSONALITY HANDLING
P: Christoph Hellwig
M: hch@infradead.org
@@ -2767,6 +2773,12 @@ P: Deepak Saxena
M: dsaxena@plexity.net
S: Maintained
+TASKSTATS STATISTICS INTERFACE
+P: Shailabh Nagar
+M: nagar@watson.ibm.com
+L: linux-kernel@vger.kernel.org
+S: Maintained
+
TI PARALLEL LINK CABLE DRIVER
P: Romain Lievin
M: roms@lpg.ticalc.org
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3c5610ca0c9..6afa72e080c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -463,6 +463,10 @@ struct signal_struct {
#ifdef CONFIG_BSD_PROCESS_ACCT
struct pacct_struct pacct; /* per-process accounting information */
#endif
+#ifdef CONFIG_TASKSTATS
+ spinlock_t stats_lock;
+ struct taskstats *stats;
+#endif
};
/* Context switch must be unlocked if interrupts are to be enabled */
diff --git a/include/linux/taskstats_kern.h b/include/linux/taskstats_kern.h
index fc9da2e2644..0ae8f67af1f 100644
--- a/include/linux/taskstats_kern.h
+++ b/include/linux/taskstats_kern.h
@@ -19,36 +19,75 @@ enum {
extern kmem_cache_t *taskstats_cache;
extern struct mutex taskstats_exit_mutex;
-static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
- struct taskstats **ptgidstats)
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats)
{
*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)
+static inline void taskstats_exit_free(struct taskstats *tidstats)
{
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);
+static inline void taskstats_tgid_init(struct signal_struct *sig)
+{
+ spin_lock_init(&sig->stats_lock);
+ sig->stats = NULL;
+}
+
+static inline void taskstats_tgid_alloc(struct signal_struct *sig)
+{
+ struct taskstats *stats;
+ unsigned long flags;
+
+ stats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);
+ if (!stats)
+ return;
+
+ spin_lock_irqsave(&sig->stats_lock, flags);
+ if (!sig->stats) {
+ sig->stats = stats;
+ stats = NULL;
+ }
+ spin_unlock_irqrestore(&sig->stats_lock, flags);
+
+ if (stats)
+ kmem_cache_free(taskstats_cache, stats);
+}
+static inline void taskstats_tgid_free(struct signal_struct *sig)
+{
+ struct taskstats *stats = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&sig->stats_lock, flags);
+ if (sig->stats) {
+ stats = sig->stats;
+ sig->stats = NULL;
+ }
+ spin_unlock_irqrestore(&sig->stats_lock, flags);
+ if (stats)
+ kmem_cache_free(taskstats_cache, stats);
+}
+
+extern void taskstats_exit_send(struct task_struct *, struct taskstats *, int);
+extern void taskstats_init_early(void);
+extern void taskstats_tgid_alloc(struct signal_struct *);
#else
-static inline void taskstats_exit_alloc(struct taskstats **ptidstats,
- struct taskstats **ptgidstats)
+static inline void taskstats_exit_alloc(struct taskstats **ptidstats)
{}
-static inline void taskstats_exit_free(struct taskstats *ptidstats,
- struct taskstats *ptgidstats)
+static inline void taskstats_exit_free(struct taskstats *ptidstats)
{}
static inline void taskstats_exit_send(struct task_struct *tsk,
- struct taskstats *tidstats,
- struct taskstats *tgidstats)
+ struct taskstats *tidstats,
+ int group_dead)
+{}
+static inline void taskstats_tgid_init(struct signal_struct *sig)
+{}
+static inline void taskstats_tgid_alloc(struct signal_struct *sig)
+{}
+static inline void taskstats_tgid_free(struct signal_struct *sig)
{}
static inline void taskstats_init_early(void)
{}
diff --git a/kernel/exit.c b/kernel/exit.c
index 9852ed8c298..67c1e9a4f81 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -845,7 +845,7 @@ static void exit_notify(struct task_struct *tsk)
fastcall NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
- struct taskstats *tidstats, *tgidstats;
+ struct taskstats *tidstats;
int group_dead;
profile_task_exit(tsk);
@@ -884,7 +884,7 @@ fastcall NORET_TYPE void do_exit(long code)
current->comm, current->pid,
preempt_count());
- taskstats_exit_alloc(&tidstats, &tgidstats);
+ taskstats_exit_alloc(&tidstats);
acct_update_integrals(tsk);
if (tsk->mm) {
@@ -905,8 +905,8 @@ fastcall NORET_TYPE void do_exit(long code)
#endif
if (unlikely(tsk->audit_context))
audit_free(tsk);
- taskstats_exit_send(tsk, tidstats, tgidstats);
- taskstats_exit_free(tidstats, tgidstats);
+ taskstats_exit_send(tsk, tidstats, group_dead);
+ taskstats_exit_free(tidstats);
delayacct_tsk_exit(tsk);
exit_mm(tsk);
diff --git a/kernel/fork.c b/kernel/fork.c
index 451cfd35bf2..1b0f7b1e088 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -44,6 +44,7 @@
#include <linux/acct.h>
#include <linux/cn_proc.h>
#include <linux/delayacct.h>
+#include <linux/taskstats_kern.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -819,6 +820,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
if (clone_flags & CLONE_THREAD) {
atomic_inc(&current->signal->count);
atomic_inc(&current->signal->live);
+ taskstats_tgid_alloc(current->signal);
return 0;
}
sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
@@ -863,6 +865,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
INIT_LIST_HEAD(&sig->cpu_timers[0]);
INIT_LIST_HEAD(&sig->cpu_timers[1]);
INIT_LIST_HEAD(&sig->cpu_timers[2]);
+ taskstats_tgid_init(sig);
task_lock(current->group_leader);
memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
@@ -884,6 +887,7 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
void __cleanup_signal(struct signal_struct *sig)
{
exit_thread_group_keys(sig);
+ taskstats_tgid_free(sig);
kmem_cache_free(signal_cachep, sig);
}
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index ea9506de3b8..4a0a5022b29 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -132,46 +132,79 @@ static int fill_pid(pid_t pid, struct task_struct *pidtsk,
static int fill_tgid(pid_t tgid, struct task_struct *tgidtsk,
struct taskstats *stats)
{
- int rc;
struct task_struct *tsk, *first;
+ unsigned long flags;
+ /*
+ * Add additional stats from live tasks except zombie thread group
+ * leaders who are already counted with the dead tasks
+ */
first = tgidtsk;
- read_lock(&tasklist_lock);
if (!first) {
+ read_lock(&tasklist_lock);
first = find_task_by_pid(tgid);
if (!first) {
read_unlock(&tasklist_lock);
return -ESRCH;
}
- }
+ get_task_struct(first);
+ read_unlock(&tasklist_lock);
+ } else
+ get_task_struct(first);
+
+ /* Start with stats from dead tasks */
+ spin_lock_irqsave(&first->signal->stats_lock, flags);
+ if (first->signal->stats)
+ memcpy(stats, first->signal->stats, sizeof(*stats));
+ spin_unlock_irqrestore(&first->signal->stats_lock, flags);
+
tsk = first;
+ read_lock(&tasklist_lock);
do {
+ if (tsk->exit_state == EXIT_ZOMBIE && thread_group_leader(tsk))
+ continue;
/*
- * Each accounting subsystem adds calls its functions to
+ * Accounting subsystem can call its functions here to
* fill in relevant parts of struct taskstsats as follows
*
- * rc = per-task-foo(stats, tsk);
- * if (rc)
- * break;
+ * per-task-foo(stats, tsk);
*/
-
- rc = delayacct_add_tsk(stats, tsk);
- if (rc)
- break;
+ delayacct_add_tsk(stats, tsk);
} while_each_thread(first, tsk);
read_unlock(&tasklist_lock);
stats->version = TASKSTATS_VERSION;
-
/*
- * Accounting subsytems can also add calls here if they don't
- * wish to aggregate statistics for per-tgid stats
+ * Accounting subsytems can also add calls here to modify
+ * fields of taskstats.
*/
- return rc;
+ return 0;
+}
+
+
+static void fill_tgid_exit(struct task_struct *tsk)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&tsk->signal->stats_lock, flags);
+ if (!tsk->signal->stats)
+ goto ret;
+
+ /*
+ * Each accounting subsystem calls its functions here to
+ * accumalate its per-task stats for tsk, into the per-tgid structure
+ *
+ * per-task-foo(tsk->signal->stats, tsk);
+ */
+ delayacct_add_tsk(tsk->signal->stats, tsk);
+ret:
+ spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
+ return;
}
+
static int taskstats_send_stats(struct sk_buff *skb, struct genl_info *info)
{
int rc = 0;
@@ -230,7 +263,7 @@ err:
/* Send pid data out on exit */
void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
- struct taskstats *tgidstats)
+ int group_dead)
{
int rc;
struct sk_buff *rep_skb;
@@ -238,13 +271,16 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
size_t size;
int is_thread_group;
struct nlattr *na;
+ unsigned long flags;
if (!family_registered || !tidstats)
return;
- is_thread_group = !thread_group_empty(tsk);
- rc = 0;
+ spin_lock_irqsave(&tsk->signal->stats_lock, flags);
+ is_thread_group = tsk->signal->stats ? 1 : 0;
+ spin_unlock_irqrestore(&tsk->signal->stats_lock, flags);
+ rc = 0;
/*
* Size includes space for nested attributes
*/
@@ -268,30 +304,28 @@ void taskstats_exit_send(struct task_struct *tsk, struct taskstats *tidstats,
*tidstats);
nla_nest_end(rep_skb, na);
- if (!is_thread_group || !tgidstats) {
- send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
- goto ret;
- }
+ if (!is_thread_group)
+ goto send;
- 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.
+ * tsk has/had a thread group so fill the tsk->signal->stats structure
+ * Doesn't matter if tsk is the leader or the last group member leaving
*/
- if (rc < 0) {
- send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
- goto ret;
- }
+
+ fill_tgid_exit(tsk);
+ if (!group_dead)
+ goto send;
na = nla_nest_start(rep_skb, TASKSTATS_TYPE_AGGR_TGID);
NLA_PUT_U32(rep_skb, TASKSTATS_TYPE_TGID, (u32)tsk->tgid);
+ /* No locking needed for tsk->signal->stats since group is dead */
NLA_PUT_TYPE(rep_skb, struct taskstats, TASKSTATS_TYPE_STATS,
- *tgidstats);
+ *tsk->signal->stats);
nla_nest_end(rep_skb, na);
+send:
send_reply(rep_skb, 0, TASKSTATS_MSG_MULTICAST);
- goto ret;
+ return;
nla_put_failure:
genlmsg_cancel(rep_skb, reply);