tracing: Remove obsolete sched_switch tracer (87d80de2) · Commits · 方亚芬 / linux

Documentation/trace/ftrace.txt

+0 −110

Original line number	Diff line number	Diff line
		@@ -202,10 +202,6 @@ Here is the list of current tracers that may be configured.
		to draw a graph of function calls similar to C code
		source.

		"sched_switch"

		Traces the context switches and wakeups between tasks.

		"irqsoff"

		Traces the areas that disable interrupts and saves
		@@ -273,39 +269,6 @@ format, the function name that was traced "path_put" and the
		parent function that called this function "path_walk". The
		timestamp is the time at which the function was entered.

		The sched_switch tracer also includes tracing of task wakeups
		and context switches.

		ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 2916:115:S
		ksoftirqd/1-7 [01] 1453.070013: 7:115:R + 10:115:S
		ksoftirqd/1-7 [01] 1453.070013: 7:115:R ==> 10:115:R
		events/1-10 [01] 1453.070013: 10:115:S ==> 2916:115:R
		kondemand/1-2916 [01] 1453.070013: 2916:115:S ==> 7:115:R
		ksoftirqd/1-7 [01] 1453.070013: 7:115:S ==> 0:140:R

		Wake ups are represented by a "+" and the context switches are
		shown as "==>". The format is:

		Context switches:

		Previous task Next Task

		<pid>:<prio>:<state> ==> <pid>:<prio>:<state>

		Wake ups:

		Current task Task waking up

		<pid>:<prio>:<state> + <pid>:<prio>:<state>

		The prio is the internal kernel priority, which is the inverse
		of the priority that is usually displayed by user-space tools.
		Zero represents the highest priority (99). Prio 100 starts the
		"nice" priorities with 100 being equal to nice -20 and 139 being
		nice 19. The prio "140" is reserved for the idle task which is
		the lowest priority thread (pid 0).


		Latency trace format
		--------------------

		@@ -491,79 +454,6 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
		latencies, as described in "Latency
		trace format".

		sched_switch
		------------

		This tracer simply records schedule switches. Here is an example
		of how to use it.

		# echo sched_switch > current_tracer
		# echo 1 > tracing_enabled
		# sleep 1
		# echo 0 > tracing_enabled
		# cat trace

		# tracer: sched_switch
		#
		# TASK-PID CPU# TIMESTAMP FUNCTION
		# \| \| \| \| \|
		bash-3997 [01] 240.132281: 3997:120:R + 4055:120:R
		bash-3997 [01] 240.132284: 3997:120:R ==> 4055:120:R
		sleep-4055 [01] 240.132371: 4055:120:S ==> 3997:120:R
		bash-3997 [01] 240.132454: 3997:120:R + 4055:120:S
		bash-3997 [01] 240.132457: 3997:120:R ==> 4055:120:R
		sleep-4055 [01] 240.132460: 4055:120:D ==> 3997:120:R
		bash-3997 [01] 240.132463: 3997:120:R + 4055:120:D
		bash-3997 [01] 240.132465: 3997:120:R ==> 4055:120:R
		<idle>-0 [00] 240.132589: 0:140:R + 4:115:S
		<idle>-0 [00] 240.132591: 0:140:R ==> 4:115:R
		ksoftirqd/0-4 [00] 240.132595: 4:115:S ==> 0:140:R
		<idle>-0 [00] 240.132598: 0:140:R + 4:115:S
		<idle>-0 [00] 240.132599: 0:140:R ==> 4:115:R
		ksoftirqd/0-4 [00] 240.132603: 4:115:S ==> 0:140:R
		sleep-4055 [01] 240.133058: 4055:120:S ==> 3997:120:R
		[...]


		As we have discussed previously about this format, the header
		shows the name of the trace and points to the options. The
		"FUNCTION" is a misnomer since here it represents the wake ups
		and context switches.

		The sched_switch file only lists the wake ups (represented with
		'+') and context switches ('==>') with the previous task or
		current task first followed by the next task or task waking up.
		The format for both of these is PID:KERNEL-PRIO:TASK-STATE.
		Remember that the KERNEL-PRIO is the inverse of the actual
		priority with zero (0) being the highest priority and the nice
		values starting at 100 (nice -20). Below is a quick chart to map
		the kernel priority to user land priorities.

		Kernel Space User Space
		===============================================================
		0(high) to 98(low) user RT priority 99(high) to 1(low)
		with SCHED_RR or SCHED_FIFO
		---------------------------------------------------------------
		99 sched_priority is not used in scheduling
		decisions(it must be specified as 0)
		---------------------------------------------------------------
		100(high) to 139(low) user nice -20(high) to 19(low)
		---------------------------------------------------------------
		140 idle task priority
		---------------------------------------------------------------

		The task states are:

		R - running : wants to run, may not actually be running
		S - sleep : process is waiting to be woken up (handles signals)
		D - disk sleep (uninterruptible sleep) : process must be woken up
		(ignores signals)
		T - stopped : process suspended
		t - traced : process is being traced (with something like gdb)
		Z - zombie : process waiting to be cleaned up
		X - unknown


		ftrace_enabled
		--------------

kernel/trace/trace_sched_switch.c

+0 −48

Original line number	Diff line number	Diff line
		@@ -247,51 +247,3 @@ void tracing_sched_switch_assign_trace(struct trace_array *tr)
		ctx_trace = tr;
		}

		static void stop_sched_trace(struct trace_array *tr)
		{
		tracing_stop_sched_switch_record();
		}

		static int sched_switch_trace_init(struct trace_array *tr)
		{
		ctx_trace = tr;
		tracing_reset_online_cpus(tr);
		tracing_start_sched_switch_record();
		return 0;
		}

		static void sched_switch_trace_reset(struct trace_array *tr)
		{
		if (sched_ref)
		stop_sched_trace(tr);
		}

		static void sched_switch_trace_start(struct trace_array *tr)
		{
		sched_stopped = 0;
		}

		static void sched_switch_trace_stop(struct trace_array *tr)
		{
		sched_stopped = 1;
		}

		static struct tracer sched_switch_trace __read_mostly =
		{
		.name = "sched_switch",
		.init = sched_switch_trace_init,
		.reset = sched_switch_trace_reset,
		.start = sched_switch_trace_start,
		.stop = sched_switch_trace_stop,
		.wait_pipe = poll_wait_pipe,
		#ifdef CONFIG_FTRACE_SELFTEST
		.selftest = trace_selftest_startup_sched_switch,
		#endif
		};

		__init static int init_sched_switch_trace(void)
		{
		return register_tracer(&sched_switch_trace);
		}
		device_initcall(init_sched_switch_trace);