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Commit af4617bd authored by Steven Rostedt's avatar Steven Rostedt
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tracing: add global-clock option to provide cross CPU clock to traces 



Impact: feature to allow better serialized clock

This patch adds an option called "global-clock" that will allow
the tracer to switch to a slower but more accurate (across CPUs)
clock.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 37886f6a

kernel/trace/trace.c

+30 −4
Original line number Diff line number Diff line
@@ -315,6 +315,7 @@ static const char *trace_options[] = { 
	"printk-msg-only",

	"context-info",

	"latency-format",

	"global-clock",

	NULL

};
@@ -2251,6 +2252,34 @@ static int set_tracer_option(struct tracer *trace, char *cmp, int neg) 
	return 0;

}



static void set_tracer_flags(unsigned int mask, int enabled)

{

	/* do nothing if flag is already set */

	if (!!(trace_flags & mask) == !!enabled)

		return;



	if (enabled)

		trace_flags |= mask;

	else

		trace_flags &= ~mask;



	if (mask == TRACE_ITER_GLOBAL_CLK) {

		u64 (*func)(void);



		if (enabled)

			func = trace_clock_global;

		else

			func = trace_clock_local;



		mutex_lock(&trace_types_lock);

		ring_buffer_set_clock(global_trace.buffer, func);



		if (max_tr.buffer)

			ring_buffer_set_clock(max_tr.buffer, func);

		mutex_unlock(&trace_types_lock);

	}

}



static ssize_t

tracing_trace_options_write(struct file *filp, const char __user *ubuf,

			size_t cnt, loff_t *ppos)
@@ -2278,10 +2307,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf, 
		int len = strlen(trace_options[i]);



		if (strncmp(cmp, trace_options[i], len) == 0) {

			if (neg)

				trace_flags &= ~(1 << i);

			else

				trace_flags |= (1 << i);

			set_tracer_flags(1 << i, !neg);

			break;

		}

	}

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -667,6 +667,7 @@ enum trace_iterator_flags { 
	TRACE_ITER_PRINTK_MSGONLY	= 0x10000,

	TRACE_ITER_CONTEXT_INFO		= 0x20000, /* Print pid/cpu/time */

	TRACE_ITER_LATENCY_FMT		= 0x40000,

	TRACE_ITER_GLOBAL_CLK		= 0x80000,

};



/*