Merge branch 'perfcounters-fixes-for-linus' of... (d00aa669) · Commits · 戴 / test

arch/powerpc/kernel/perf_counter.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -518,6 +518,8 @@ void hw_perf_disable(void)
		struct cpu_hw_counters *cpuhw;
		unsigned long flags;

		if (!ppmu)
		return;
		local_irq_save(flags);
		cpuhw = &__get_cpu_var(cpu_hw_counters);

		@@ -572,6 +574,8 @@ void hw_perf_enable(void)
		int n_lim;
		int idx;

		if (!ppmu)
		return;
		local_irq_save(flags);
		cpuhw = &__get_cpu_var(cpu_hw_counters);
		if (!cpuhw->disabled) {
		@@ -737,6 +741,8 @@ int hw_perf_group_sched_in(struct perf_counter *group_leader,
		long i, n, n0;
		struct perf_counter *sub;

		if (!ppmu)
		return 0;
		cpuhw = &__get_cpu_var(cpu_hw_counters);
		n0 = cpuhw->n_counters;
		n = collect_events(group_leader, ppmu->n_counter - n0,
		@@ -1281,6 +1287,8 @@ void hw_perf_counter_setup(int cpu)
		{
		struct cpu_hw_counters *cpuhw = &per_cpu(cpu_hw_counters, cpu);

		if (!ppmu)
		return;
		memset(cpuhw, 0, sizeof(*cpuhw));
		cpuhw->mmcr[0] = MMCR0_FC;
		}

include/linux/perf_counter.h

+7 −5

Original line number	Diff line number	Diff line
		@@ -121,7 +121,7 @@ enum perf_counter_sample_format {
		PERF_SAMPLE_CPU = 1U << 7,
		PERF_SAMPLE_PERIOD = 1U << 8,
		PERF_SAMPLE_STREAM_ID = 1U << 9,
		PERF_SAMPLE_TP_RECORD = 1U << 10,
		PERF_SAMPLE_RAW = 1U << 10,

		PERF_SAMPLE_MAX = 1U << 11, /* non-ABI */
		};
		@@ -369,6 +369,8 @@ enum perf_event_type {
		*
		* { u64 nr,
		* u64 ips[nr]; } && PERF_SAMPLE_CALLCHAIN
		* { u32 size;
		* char data[size];}&& PERF_SAMPLE_RAW
		* };
		*/
		PERF_EVENT_SAMPLE = 9,
		@@ -414,9 +416,9 @@ struct perf_callchain_entry {
		__u64 ip[PERF_MAX_STACK_DEPTH];
		};

		struct perf_tracepoint_record {
		int size;
		char *record;
		struct perf_raw_record {
		u32 size;
		void *data;
		};

		struct task_struct;
		@@ -687,7 +689,7 @@ struct perf_sample_data {
		struct pt_regs *regs;
		u64 addr;
		u64 period;
		void *private;
		struct perf_raw_record *raw;
		};

		extern int perf_counter_overflow(struct perf_counter *counter, int nmi,

include/trace/ftrace.h

+13 −2

Original line number	Diff line number	Diff line
		@@ -637,12 +637,20 @@ __attribute__((section("_ftrace_events"))) event_##call = { \
		* pc = preempt_count();
		*
		* __data_size = ftrace_get_offsets_<call>(&__data_offsets, args);
		* __entry_size = __data_size + sizeof(*entry);
		*
		* // Below we want to get the aligned size by taking into account
		* // the u32 field that will later store the buffer size
		* __entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),
		* sizeof(u64));
		* __entry_size -= sizeof(u32);
		*
		* do {
		* char raw_data[__entry_size]; <- allocate our sample in the stack
		* struct trace_entry *ent;
		*
		* zero dead bytes from alignment to avoid stack leak to userspace:
		*
		* (u64 )(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;
		* entry = (struct ftrace_raw_<call> *)raw_data;
		* ent = &entry->ent;
		* tracing_generic_entry_update(ent, irq_flags, pc);
		@@ -685,12 +693,15 @@ static void ftrace_profile_##call(proto) \
		pc = preempt_count(); \
		\
		__data_size = ftrace_get_offsets_##call(&__data_offsets, args); \
		__entry_size = ALIGN(__data_size + sizeof(*entry), sizeof(u64));\
		__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\
		sizeof(u64)); \
		__entry_size -= sizeof(u32); \
		\
		do { \
		char raw_data[__entry_size]; \
		struct trace_entry *ent; \
		\
		(u64 )(&raw_data[__entry_size - sizeof(u64)]) = 0ULL; \
		entry = (struct ftrace_raw_##call *)raw_data; \
		ent = &entry->ent; \
		tracing_generic_entry_update(ent, irq_flags, pc); \

kernel/perf_counter.c

+145 −94

Original line number	Diff line number	Diff line
		@@ -2646,7 +2646,6 @@ static void perf_counter_output(struct perf_counter *counter, int nmi,
		u64 counter;
		} group_entry;
		struct perf_callchain_entry *callchain = NULL;
		struct perf_tracepoint_record *tp;
		int callchain_size = 0;
		u64 time;
		struct {
		@@ -2715,9 +2714,16 @@ static void perf_counter_output(struct perf_counter *counter, int nmi,
		header.size += sizeof(u64);
		}

		if (sample_type & PERF_SAMPLE_TP_RECORD) {
		tp = data->private;
		header.size += tp->size;
		if (sample_type & PERF_SAMPLE_RAW) {
		int size = sizeof(u32);

		if (data->raw)
		size += data->raw->size;
		else
		size += sizeof(u32);

		WARN_ON_ONCE(size & (sizeof(u64)-1));
		header.size += size;
		}

		ret = perf_output_begin(&handle, counter, header.size, nmi, 1);
		@@ -2783,8 +2789,21 @@ static void perf_counter_output(struct perf_counter *counter, int nmi,
		}
		}

		if (sample_type & PERF_SAMPLE_TP_RECORD)
		perf_output_copy(&handle, tp->record, tp->size);
		if (sample_type & PERF_SAMPLE_RAW) {
		if (data->raw) {
		perf_output_put(&handle, data->raw->size);
		perf_output_copy(&handle, data->raw->data, data->raw->size);
		} else {
		struct {
		u32 size;
		u32 data;
		} raw = {
		.size = sizeof(u32),
		.data = 0,
		};
		perf_output_put(&handle, raw);
		}
		}

		perf_output_end(&handle);
		}
		@@ -2850,6 +2869,7 @@ perf_counter_read_event(struct perf_counter *counter,

		struct perf_task_event {
		struct task_struct *task;
		struct perf_counter_context *task_ctx;

		struct {
		struct perf_event_header header;
		@@ -2909,24 +2929,23 @@ static void perf_counter_task_ctx(struct perf_counter_context *ctx,
		static void perf_counter_task_event(struct perf_task_event *task_event)
		{
		struct perf_cpu_context *cpuctx;
		struct perf_counter_context *ctx;
		struct perf_counter_context *ctx = task_event->task_ctx;

		cpuctx = &get_cpu_var(perf_cpu_context);
		perf_counter_task_ctx(&cpuctx->ctx, task_event);
		put_cpu_var(perf_cpu_context);

		rcu_read_lock();
		/*
		* doesn't really matter which of the child contexts the
		* events ends up in.
		*/
		ctx = rcu_dereference(current->perf_counter_ctxp);
		if (!ctx)
		ctx = rcu_dereference(task_event->task->perf_counter_ctxp);
		if (ctx)
		perf_counter_task_ctx(ctx, task_event);
		rcu_read_unlock();
		}

		static void perf_counter_task(struct task_struct *task, int new)
		static void perf_counter_task(struct task_struct *task,
		struct perf_counter_context *task_ctx,
		int new)
		{
		struct perf_task_event task_event;

		@@ -2937,6 +2956,7 @@ static void perf_counter_task(struct task_struct *task, int new)

		task_event = (struct perf_task_event){
		.task = task,
		.task_ctx = task_ctx,
		.event = {
		.header = {
		.type = new ? PERF_EVENT_FORK : PERF_EVENT_EXIT,
		@@ -2955,7 +2975,7 @@ static void perf_counter_task(struct task_struct *task, int new)

		void perf_counter_fork(struct task_struct *task)
		{
		perf_counter_task(task, 1);
		perf_counter_task(task, NULL, 1);
		}

		/*
		@@ -3344,87 +3364,81 @@ int perf_counter_overflow(struct perf_counter *counter, int nmi,
		* Generic software counter infrastructure
		*/

		static void perf_swcounter_update(struct perf_counter *counter)
		/*
		* We directly increment counter->count and keep a second value in
		* counter->hw.period_left to count intervals. This period counter
		* is kept in the range [-sample_period, 0] so that we can use the
		* sign as trigger.
		*/

		static u64 perf_swcounter_set_period(struct perf_counter *counter)
		{
		struct hw_perf_counter *hwc = &counter->hw;
		u64 prev, now;
		s64 delta;
		u64 period = hwc->last_period;
		u64 nr, offset;
		s64 old, val;

		hwc->last_period = hwc->sample_period;

		again:
		prev = atomic64_read(&hwc->prev_count);
		now = atomic64_read(&hwc->count);
		if (atomic64_cmpxchg(&hwc->prev_count, prev, now) != prev)
		goto again;
		old = val = atomic64_read(&hwc->period_left);
		if (val < 0)
		return 0;

		delta = now - prev;
		nr = div64_u64(period + val, period);
		offset = nr * period;
		val -= offset;
		if (atomic64_cmpxchg(&hwc->period_left, old, val) != old)
		goto again;

		atomic64_add(delta, &counter->count);
		atomic64_sub(delta, &hwc->period_left);
		return nr;
		}

		static void perf_swcounter_set_period(struct perf_counter *counter)
		static void perf_swcounter_overflow(struct perf_counter *counter,
		int nmi, struct perf_sample_data *data)
		{
		struct hw_perf_counter *hwc = &counter->hw;
		s64 left = atomic64_read(&hwc->period_left);
		s64 period = hwc->sample_period;
		u64 overflow;

		if (unlikely(left <= -period)) {
		left = period;
		atomic64_set(&hwc->period_left, left);
		hwc->last_period = period;
		}
		data->period = counter->hw.last_period;
		overflow = perf_swcounter_set_period(counter);

		if (unlikely(left <= 0)) {
		left += period;
		atomic64_add(period, &hwc->period_left);
		hwc->last_period = period;
		}
		if (hwc->interrupts == MAX_INTERRUPTS)
		return;

		atomic64_set(&hwc->prev_count, -left);
		atomic64_set(&hwc->count, -left);
		for (; overflow; overflow--) {
		if (perf_counter_overflow(counter, nmi, data)) {
		/*
		* We inhibit the overflow from happening when
		* hwc->interrupts == MAX_INTERRUPTS.
		*/
		break;
		}
		}
		}

		static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
		static void perf_swcounter_unthrottle(struct perf_counter *counter)
		{
		enum hrtimer_restart ret = HRTIMER_RESTART;
		struct perf_sample_data data;
		struct perf_counter *counter;
		u64 period;

		counter = container_of(hrtimer, struct perf_counter, hw.hrtimer);
		counter->pmu->read(counter);

		data.addr = 0;
		data.regs = get_irq_regs();
		/*
		* In case we exclude kernel IPs or are somehow not in interrupt
		* context, provide the next best thing, the user IP.
		* Nothing to do, we already reset hwc->interrupts.
		*/
		if ((counter->attr.exclude_kernel \|\| !data.regs) &&
		!counter->attr.exclude_user)
		data.regs = task_pt_regs(current);

		if (data.regs) {
		if (perf_counter_overflow(counter, 0, &data))
		ret = HRTIMER_NORESTART;
		}

		period = max_t(u64, 10000, counter->hw.sample_period);
		hrtimer_forward_now(hrtimer, ns_to_ktime(period));

		return ret;
		}

		static void perf_swcounter_overflow(struct perf_counter *counter,
		static void perf_swcounter_add(struct perf_counter *counter, u64 nr,
		int nmi, struct perf_sample_data *data)
		{
		data->period = counter->hw.last_period;
		struct hw_perf_counter *hwc = &counter->hw;

		perf_swcounter_update(counter);
		perf_swcounter_set_period(counter);
		if (perf_counter_overflow(counter, nmi, data))
		/* soft-disable the counter */
		;
		atomic64_add(nr, &counter->count);

		if (!hwc->sample_period)
		return;

		if (!data->regs)
		return;

		if (!atomic64_add_negative(nr, &hwc->period_left))
		perf_swcounter_overflow(counter, nmi, data);
		}

		static int perf_swcounter_is_counting(struct perf_counter *counter)
		@@ -3488,15 +3502,6 @@ static int perf_swcounter_match(struct perf_counter *counter,
		return 1;
		}

		static void perf_swcounter_add(struct perf_counter *counter, u64 nr,
		int nmi, struct perf_sample_data *data)
		{
		int neg = atomic64_add_negative(nr, &counter->hw.count);

		if (counter->hw.sample_period && !neg && data->regs)
		perf_swcounter_overflow(counter, nmi, data);
		}

		static void perf_swcounter_ctx_event(struct perf_counter_context *ctx,
		enum perf_type_id type,
		u32 event, u64 nr, int nmi,
		@@ -3575,26 +3580,65 @@ void __perf_swcounter_event(u32 event, u64 nr, int nmi,

		static void perf_swcounter_read(struct perf_counter *counter)
		{
		perf_swcounter_update(counter);
		}

		static int perf_swcounter_enable(struct perf_counter *counter)
		{
		struct hw_perf_counter *hwc = &counter->hw;

		if (hwc->sample_period) {
		hwc->last_period = hwc->sample_period;
		perf_swcounter_set_period(counter);
		}
		return 0;
		}

		static void perf_swcounter_disable(struct perf_counter *counter)
		{
		perf_swcounter_update(counter);
		}

		static const struct pmu perf_ops_generic = {
		.enable = perf_swcounter_enable,
		.disable = perf_swcounter_disable,
		.read = perf_swcounter_read,
		.unthrottle = perf_swcounter_unthrottle,
		};

		/*
		* hrtimer based swcounter callback
		*/

		static enum hrtimer_restart perf_swcounter_hrtimer(struct hrtimer *hrtimer)
		{
		enum hrtimer_restart ret = HRTIMER_RESTART;
		struct perf_sample_data data;
		struct perf_counter *counter;
		u64 period;

		counter = container_of(hrtimer, struct perf_counter, hw.hrtimer);
		counter->pmu->read(counter);

		data.addr = 0;
		data.regs = get_irq_regs();
		/*
		* In case we exclude kernel IPs or are somehow not in interrupt
		* context, provide the next best thing, the user IP.
		*/
		if ((counter->attr.exclude_kernel \|\| !data.regs) &&
		!counter->attr.exclude_user)
		data.regs = task_pt_regs(current);

		if (data.regs) {
		if (perf_counter_overflow(counter, 0, &data))
		ret = HRTIMER_NORESTART;
		}

		period = max_t(u64, 10000, counter->hw.sample_period);
		hrtimer_forward_now(hrtimer, ns_to_ktime(period));

		return ret;
		}

		/*
		* Software counter: cpu wall time clock
		*/
		@@ -3715,15 +3759,15 @@ static const struct pmu perf_ops_task_clock = {
		void perf_tpcounter_event(int event_id, u64 addr, u64 count, void *record,
		int entry_size)
		{
		struct perf_tracepoint_record tp = {
		struct perf_raw_record raw = {
		.size = entry_size,
		.record = record,
		.data = record,
		};

		struct perf_sample_data data = {
		.regs = get_irq_regs(),
		.addr = addr,
		.private = &tp,
		.raw = &raw,
		};

		if (!data.regs)
		@@ -3743,6 +3787,14 @@ static void tp_perf_counter_destroy(struct perf_counter *counter)

		static const struct pmu tp_perf_counter_init(struct perf_counter counter)
		{
		/*
		* Raw tracepoint data is a severe data leak, only allow root to
		* have these.
		*/
		if ((counter->attr.sample_type & PERF_SAMPLE_RAW) &&
		!capable(CAP_SYS_ADMIN))
		return ERR_PTR(-EPERM);

		if (ftrace_profile_enable(counter->attr.config))
		return NULL;

		@@ -4285,7 +4337,7 @@ void perf_counter_exit_task(struct task_struct *child)
		unsigned long flags;

		if (likely(!child->perf_counter_ctxp)) {
		perf_counter_task(child, 0);
		perf_counter_task(child, NULL, 0);
		return;
		}

		@@ -4305,6 +4357,7 @@ void perf_counter_exit_task(struct task_struct *child)
		* incremented the context's refcount before we do put_ctx below.
		*/
		spin_lock(&child_ctx->lock);
		child->perf_counter_ctxp = NULL;
		/*
		* If this context is a clone; unclone it so it can't get
		* swapped to another process while we're removing all
		@@ -4318,9 +4371,7 @@ void perf_counter_exit_task(struct task_struct *child)
		* won't get any samples after PERF_EVENT_EXIT. We can however still
		* get a few PERF_EVENT_READ events.
		*/
		perf_counter_task(child, 0);

		child->perf_counter_ctxp = NULL;
		perf_counter_task(child, child_ctx, 0);

		/*
		* We can recurse on the same lock type through:

tools/perf/Documentation/perf-examples.txt

0 → 100644

+225 −0

Original line number	Diff line number	Diff line

		------------------------------
		**** perf by examples ****
		------------------------------

		[ From an e-mail by Ingo Molnar, http://lkml.org/lkml/2009/8/4/346 ]


		First, discovery/enumeration of available counters can be done via
		'perf list':

		titan:~> perf list
		[...]
		kmem:kmalloc [Tracepoint event]
		kmem:kmem_cache_alloc [Tracepoint event]
		kmem:kmalloc_node [Tracepoint event]
		kmem:kmem_cache_alloc_node [Tracepoint event]
		kmem:kfree [Tracepoint event]
		kmem:kmem_cache_free [Tracepoint event]
		kmem:mm_page_free_direct [Tracepoint event]
		kmem:mm_pagevec_free [Tracepoint event]
		kmem:mm_page_alloc [Tracepoint event]
		kmem:mm_page_alloc_zone_locked [Tracepoint event]
		kmem:mm_page_pcpu_drain [Tracepoint event]
		kmem:mm_page_alloc_extfrag [Tracepoint event]

		Then any (or all) of the above event sources can be activated and
		measured. For example the page alloc/free properties of a 'hackbench
		run' are:

		titan:~> perf stat -e kmem:mm_page_pcpu_drain -e kmem:mm_page_alloc
		-e kmem:mm_pagevec_free -e kmem:mm_page_free_direct ./hackbench 10
		Time: 0.575

		Performance counter stats for './hackbench 10':

		13857 kmem:mm_page_pcpu_drain
		27576 kmem:mm_page_alloc
		6025 kmem:mm_pagevec_free
		20934 kmem:mm_page_free_direct

		0.613972165 seconds time elapsed

		You can observe the statistical properties as well, by using the
		'repeat the workload N times' feature of perf stat:

		titan:~> perf stat --repeat 5 -e kmem:mm_page_pcpu_drain -e
		kmem:mm_page_alloc -e kmem:mm_pagevec_free -e
		kmem:mm_page_free_direct ./hackbench 10
		Time: 0.627
		Time: 0.644
		Time: 0.564
		Time: 0.559
		Time: 0.626

		Performance counter stats for './hackbench 10' (5 runs):

		12920 kmem:mm_page_pcpu_drain ( +- 3.359% )
		25035 kmem:mm_page_alloc ( +- 3.783% )
		6104 kmem:mm_pagevec_free ( +- 0.934% )
		18376 kmem:mm_page_free_direct ( +- 4.941% )

		0.643954516 seconds time elapsed ( +- 2.363% )

		Furthermore, these tracepoints can be used to sample the workload as
		well. For example the page allocations done by a 'git gc' can be
		captured the following way:

		titan:~/git> perf record -f -e kmem:mm_page_alloc -c 1 ./git gc
		Counting objects: 1148, done.
		Delta compression using up to 2 threads.
		Compressing objects: 100% (450/450), done.
		Writing objects: 100% (1148/1148), done.
		Total 1148 (delta 690), reused 1148 (delta 690)
		[ perf record: Captured and wrote 0.267 MB perf.data (~11679 samples) ]

		To check which functions generated page allocations:

		titan:~/git> perf report
		# Samples: 10646
		#
		# Overhead Command Shared Object
		# ........ ............... ..........................
		#
		23.57% git-repack /lib64/libc-2.5.so
		21.81% git /lib64/libc-2.5.so
		14.59% git ./git
		11.79% git-repack ./git
		7.12% git /lib64/ld-2.5.so
		3.16% git-repack /lib64/libpthread-2.5.so
		2.09% git-repack /bin/bash
		1.97% rm /lib64/libc-2.5.so
		1.39% mv /lib64/ld-2.5.so
		1.37% mv /lib64/libc-2.5.so
		1.12% git-repack /lib64/ld-2.5.so
		0.95% rm /lib64/ld-2.5.so
		0.90% git-update-serv /lib64/libc-2.5.so
		0.73% git-update-serv /lib64/ld-2.5.so
		0.68% perf /lib64/libpthread-2.5.so
		0.64% git-repack /usr/lib64/libz.so.1.2.3

		Or to see it on a more finegrained level:

		titan:~/git> perf report --sort comm,dso,symbol
		# Samples: 10646
		#
		# Overhead Command Shared Object Symbol
		# ........ ............... .......................... ......
		#
		9.35% git-repack ./git [.] insert_obj_hash
		9.12% git ./git [.] insert_obj_hash
		7.31% git /lib64/libc-2.5.so [.] memcpy
		6.34% git-repack /lib64/libc-2.5.so [.] _int_malloc
		6.24% git-repack /lib64/libc-2.5.so [.] memcpy
		5.82% git-repack /lib64/libc-2.5.so [.] __GI___fork
		5.47% git /lib64/libc-2.5.so [.] _int_malloc
		2.99% git /lib64/libc-2.5.so [.] memset

		Furthermore, call-graph sampling can be done too, of page
		allocations - to see precisely what kind of page allocations there
		are:

		titan:~/git> perf record -f -g -e kmem:mm_page_alloc -c 1 ./git gc
		Counting objects: 1148, done.
		Delta compression using up to 2 threads.
		Compressing objects: 100% (450/450), done.
		Writing objects: 100% (1148/1148), done.
		Total 1148 (delta 690), reused 1148 (delta 690)
		[ perf record: Captured and wrote 0.963 MB perf.data (~42069 samples) ]

		titan:~/git> perf report -g
		# Samples: 10686
		#
		# Overhead Command Shared Object
		# ........ ............... ..........................
		#
		23.25% git-repack /lib64/libc-2.5.so
		\|
		\|--50.00%-- _int_free
		\|
		\|--37.50%-- __GI___fork
		\| make_child
		\|
		\|--12.50%-- ptmalloc_unlock_all2
		\| make_child
		\|
		--6.25%-- __GI_strcpy
		21.61% git /lib64/libc-2.5.so
		\|
		\|--30.00%-- __GI_read
		\| \|
		\| --83.33%-- git_config_from_file
		\| git_config
		\| \|
		[...]

		Or you can observe the whole system's page allocations for 10
		seconds:

		titan:~/git> perf stat -a -e kmem:mm_page_pcpu_drain -e
		kmem:mm_page_alloc -e kmem:mm_pagevec_free -e
		kmem:mm_page_free_direct sleep 10

		Performance counter stats for 'sleep 10':

		171585 kmem:mm_page_pcpu_drain
		322114 kmem:mm_page_alloc
		73623 kmem:mm_pagevec_free
		254115 kmem:mm_page_free_direct

		10.000591410 seconds time elapsed

		Or observe how fluctuating the page allocations are, via statistical
		analysis done over ten 1-second intervals:

		titan:~/git> perf stat --repeat 10 -a -e kmem:mm_page_pcpu_drain -e
		kmem:mm_page_alloc -e kmem:mm_pagevec_free -e
		kmem:mm_page_free_direct sleep 1

		Performance counter stats for 'sleep 1' (10 runs):

		17254 kmem:mm_page_pcpu_drain ( +- 3.709% )
		34394 kmem:mm_page_alloc ( +- 4.617% )
		7509 kmem:mm_pagevec_free ( +- 4.820% )
		25653 kmem:mm_page_free_direct ( +- 3.672% )

		1.058135029 seconds time elapsed ( +- 3.089% )

		Or you can annotate the recorded 'git gc' run on a per symbol basis
		and check which instructions/source-code generated page allocations:

		titan:~/git> perf annotate __GI___fork
		------------------------------------------------
		Percent \| Source code & Disassembly of libc-2.5.so
		------------------------------------------------
		:
		:
		: Disassembly of section .plt:
		: Disassembly of section .text:
		:
		: 00000031a2e95560 <__fork>:
		[...]
		0.00 : 31a2e95602: b8 38 00 00 00 mov $0x38,%eax
		0.00 : 31a2e95607: 0f 05 syscall
		83.42 : 31a2e95609: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax
		0.00 : 31a2e9560f: 0f 87 4d 01 00 00 ja 31a2e95762 <__fork+0x202>
		0.00 : 31a2e95615: 85 c0 test %eax,%eax

		( this shows that 83.42% of __GI___fork's page allocations come from
		the 0x38 system call it performs. )

		etc. etc. - a lot more is possible. I could list a dozen of
		other different usecases straight away - neither of which is
		possible via /proc/vmstat.

		/proc/vmstat is not in the same league really, in terms of
		expressive power of system analysis and performance
		analysis.

		All that the above results needed were those new tracepoints
		in include/tracing/events/kmem.h.

		Ingo

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