x86: Add NMI duration tracepoints (0c4df02d) · Commits · 戴 / test

Documentation/trace/events-nmi.txt

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		NMI Trace Events

		These events normally show up here:

		/sys/kernel/debug/tracing/events/nmi

		--

		nmi_handler:

		You might want to use this tracepoint if you suspect that your
		NMI handlers are hogging large amounts of CPU time. The kernel
		will warn if it sees long-running handlers:

		INFO: NMI handler took too long to run: 9.207 msecs

		and this tracepoint will allow you to drill down and get some
		more details.

		Let's say you suspect that perf_event_nmi_handler() is causing
		you some problems and you only want to trace that handler
		specifically. You need to find its address:

		$ grep perf_event_nmi_handler /proc/kallsyms
		ffffffff81625600 t perf_event_nmi_handler

		Let's also say you are only interested in when that function is
		really hogging a lot of CPU time, like a millisecond at a time.
		Note that the kernel's output is in milliseconds, but the input
		to the filter is in nanoseconds! You can filter on 'delta_ns':

		cd /sys/kernel/debug/tracing/events/nmi/nmi_handler
		echo 'handler==0xffffffff81625600 && delta_ns>1000000' > filter
		echo 1 > enable

		Your output would then look like:

		$ cat /sys/kernel/debug/tracing/trace_pipe
		<idle>-0 [000] d.h3 505.397558: nmi_handler: perf_event_nmi_handler() delta_ns: 3236765 handled: 1
		<idle>-0 [000] d.h3 505.805893: nmi_handler: perf_event_nmi_handler() delta_ns: 3174234 handled: 1
		<idle>-0 [000] d.h3 506.158206: nmi_handler: perf_event_nmi_handler() delta_ns: 3084642 handled: 1
		<idle>-0 [000] d.h3 506.334346: nmi_handler: perf_event_nmi_handler() delta_ns: 3080351 handled: 1

arch/x86/kernel/nmi.c

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Original line number	Diff line number	Diff line
		@@ -30,6 +30,9 @@
		#include <asm/nmi.h>
		#include <asm/x86_init.h>

		#define CREATE_TRACE_POINTS
		#include <trace/events/nmi.h>

		struct nmi_desc {
		spinlock_t lock;
		struct list_head head;
		@@ -108,11 +111,13 @@ static int __kprobes nmi_handle(unsigned int type, struct pt_regs *regs, bool b2
		*/
		list_for_each_entry_rcu(a, &desc->head, list) {
		u64 before, delta, whole_msecs;
		int decimal_msecs;
		int decimal_msecs, thishandled;

		before = local_clock();
		handled += a->handler(type, regs);
		thishandled = a->handler(type, regs);
		handled += thishandled;
		delta = local_clock() - before;
		trace_nmi_handler(a->handler, (int)delta, thishandled);

		if (delta < nmi_longest_ns)
		continue;

include/trace/events/nmi.h

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		#undef TRACE_SYSTEM
		#define TRACE_SYSTEM nmi

		#if !defined(_TRACE_NMI_H) \|\| defined(TRACE_HEADER_MULTI_READ)
		#define _TRACE_NMI_H

		#include <linux/ktime.h>
		#include <linux/tracepoint.h>

		TRACE_EVENT(nmi_handler,

		TP_PROTO(void *handler, s64 delta_ns, int handled),

		TP_ARGS(handler, delta_ns, handled),

		TP_STRUCT__entry(
		__field( void *, handler )
		__field( s64, delta_ns)
		__field( int, handled )
		),

		TP_fast_assign(
		__entry->handler = handler;
		__entry->delta_ns = delta_ns;
		__entry->handled = handled;
		),

		TP_printk("%ps() delta_ns: %lld handled: %d",
		__entry->handler,
		__entry->delta_ns,
		__entry->handled)
		);

		#endif /* _TRACE_NMI_H */

		/* This part ust be outside protection */
		#include <trace/define_trace.h>

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