[PATCH] delay accounting taskstats interface send tgid once (ad4ecbcb) · Commits · 戴 / test

Documentation/accounting/delay-accounting.txt

+4 −9

Original line number	Original line	Diff line number	Diff line
	@@ -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		experienced by the task waiting for the corresponding resource
	in that interval.		in that interval.

	When a task exits, records containing the per-task and per-process statistics		When a task exits, records containing the per-task statistics
	are sent to userspace without requiring a command. More details are given in		are sent to userspace without requiring a command. If it is the last exiting
	the taskstats interface description.		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		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		be run and the corresponding delay statistics to be displayed. It also serves
	@@ -107,9 +108,3 @@ IO count delay total
	0 0		0 0
	MEM count delay total		MEM count delay total
	0 0		0 0

Documentation/accounting/taskstats.txt

+13 −20

Original line number	Original line	Diff line number	Diff line
	@@ -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).		statistics for all tasks of the process (if tgid is specified).

	To obtain statistics for tasks which are exiting, userspace opens a multicast		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		netlink socket. Each time a task exits, its per-pid statistics is always sent
	each listener on the multicast socket. The first the per-pid task's statistics		by the kernel to each listener on the multicast socket. In addition, if it is
	and the second is the sum for all tasks of the process to which the task		the last thread exiting its thread group, an additional record containing the
	belongs (the task does not need to be the thread group leader). The need for		per-tgid stats are also sent. The latter contains the sum of per-pid stats for
	per-tgid stats to be sent for each exiting task is explained in the per-tgid		all threads in the thread group, both past and present.
	stats section below.

	getdelays.c is a simple utility demonstrating usage of the taskstats interface		getdelays.c is a simple utility demonstrating usage of the taskstats interface
	for reporting delay accounting statistics.		for reporting delay accounting statistics.
	@@ -104,20 +103,14 @@ stats in userspace alone is inefficient and potentially inaccurate (due to lack
	of atomicity).		of atomicity).

	However, maintaining per-process, in addition to per-task stats, within the		However, maintaining per-process, in addition to per-task stats, within the
	kernel has space and time overheads. Hence the taskstats implementation		kernel has space and time overheads. To address this, the taskstats code
	dynamically sums up the per-task stats for each task belonging to a process		accumalates each exiting task's statistics into a process-wide data structure.
	whenever per-process stats are needed.		When the last task of a process exits, the process level data accumalated also
			gets sent to userspace (along with the per-task data).
	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		When a user queries to get per-tgid data, the sum of all other live threads in
	a process exits. It isn't possible to simply return some aggregated per-process		the group is added up and added to the accumalated total for previously exited
	statistic from the kernel.		threads of the same thread group.

	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		Extending taskstats
	-------------------		-------------------

MAINTAINERS

+12 −0

Original line number	Original line	Diff line number	Diff line
	@@ -2240,6 +2240,12 @@ M: tsbogend@alpha.franken.de
	L: netdev@vger.kernel.org		L: netdev@vger.kernel.org
	S: Maintained		S: Maintained

			PER-TASK DELAY ACCOUNTING
			P: Shailabh Nagar
			M: nagar@watson.ibm.com
			L: linux-kernel@vger.kernel.org
			S: Maintained

	PERSONALITY HANDLING		PERSONALITY HANDLING
	P: Christoph Hellwig		P: Christoph Hellwig
	M: hch@infradead.org		M: hch@infradead.org
	@@ -2767,6 +2773,12 @@ P: Deepak Saxena
	M: dsaxena@plexity.net		M: dsaxena@plexity.net
	S: Maintained		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		TI PARALLEL LINK CABLE DRIVER
	P: Romain Lievin		P: Romain Lievin
	M: roms@lpg.ticalc.org		M: roms@lpg.ticalc.org

include/linux/sched.h

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -463,6 +463,10 @@ struct signal_struct {
	#ifdef CONFIG_BSD_PROCESS_ACCT		#ifdef CONFIG_BSD_PROCESS_ACCT
	struct pacct_struct pacct; /* per-process accounting information */		struct pacct_struct pacct; /* per-process accounting information */
	#endif		#endif
			#ifdef CONFIG_TASKSTATS
			spinlock_t stats_lock;
			struct taskstats *stats;
			#endif
	};		};

	/* Context switch must be unlocked if interrupts are to be enabled */		/* Context switch must be unlocked if interrupts are to be enabled */

include/linux/taskstats_kern.h

+55 −16

Original line number	Original line	Diff line number	Diff line
	@@ -19,36 +19,75 @@ enum {
	extern kmem_cache_t *taskstats_cache;		extern kmem_cache_t *taskstats_cache;
	extern struct mutex taskstats_exit_mutex;		extern struct mutex taskstats_exit_mutex;

	static inline void taskstats_exit_alloc(struct taskstats **ptidstats,		static inline void taskstats_exit_alloc(struct taskstats **ptidstats)
	struct taskstats **ptgidstats)
	{		{
	*ptidstats = kmem_cache_zalloc(taskstats_cache, SLAB_KERNEL);		*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,		static inline void taskstats_exit_free(struct taskstats *tidstats)
	struct taskstats *tgidstats)
	{		{
	if (tidstats)		if (tidstats)
	kmem_cache_free(taskstats_cache, 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 ,		static inline void taskstats_tgid_init(struct signal_struct *sig)
	struct taskstats *);		{
	extern void taskstats_init_early(void);		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		#else
	static inline void taskstats_exit_alloc(struct taskstats **ptidstats,		static inline void taskstats_exit_alloc(struct taskstats **ptidstats)
	struct taskstats **ptgidstats)
	{}		{}
	static inline void taskstats_exit_free(struct taskstats *ptidstats,		static inline void taskstats_exit_free(struct taskstats *ptidstats)
	struct taskstats *ptgidstats)
	{}		{}
	static inline void taskstats_exit_send(struct task_struct *tsk,		static inline void taskstats_exit_send(struct task_struct *tsk,
	struct taskstats *tidstats,		struct taskstats *tidstats,
	struct taskstats *tgidstats)		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)		static inline void taskstats_init_early(void)
	{}		{}

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