linux/kernel/trace/trace_entries.h
Daniel Bristot de Oliveira a955d7eac1 trace: Add timerlat tracer
The timerlat tracer aims to help the preemptive kernel developers to
found souces of wakeup latencies of real-time threads. Like cyclictest,
the tracer sets a periodic timer that wakes up a thread. The thread then
computes a *wakeup latency* value as the difference between the *current
time* and the *absolute time* that the timer was set to expire. The main
goal of timerlat is tracing in such a way to help kernel developers.

Usage

Write the ASCII text "timerlat" into the current_tracer file of the
tracing system (generally mounted at /sys/kernel/tracing).

For example:

        [root@f32 ~]# cd /sys/kernel/tracing/
        [root@f32 tracing]# echo timerlat > current_tracer

It is possible to follow the trace by reading the trace trace file:

  [root@f32 tracing]# cat trace
  # tracer: timerlat
  #
  #                              _-----=> irqs-off
  #                             / _----=> need-resched
  #                            | / _---=> hardirq/softirq
  #                            || / _--=> preempt-depth
  #                            || /
  #                            ||||             ACTIVATION
  #         TASK-PID      CPU# ||||   TIMESTAMP    ID            CONTEXT                LATENCY
  #            | |         |   ||||      |         |                  |                       |
          <idle>-0       [000] d.h1    54.029328: #1     context    irq timer_latency       932 ns
           <...>-867     [000] ....    54.029339: #1     context thread timer_latency     11700 ns
          <idle>-0       [001] dNh1    54.029346: #1     context    irq timer_latency      2833 ns
           <...>-868     [001] ....    54.029353: #1     context thread timer_latency      9820 ns
          <idle>-0       [000] d.h1    54.030328: #2     context    irq timer_latency       769 ns
           <...>-867     [000] ....    54.030330: #2     context thread timer_latency      3070 ns
          <idle>-0       [001] d.h1    54.030344: #2     context    irq timer_latency       935 ns
           <...>-868     [001] ....    54.030347: #2     context thread timer_latency      4351 ns

The tracer creates a per-cpu kernel thread with real-time priority that
prints two lines at every activation. The first is the *timer latency*
observed at the *hardirq* context before the activation of the thread.
The second is the *timer latency* observed by the thread, which is the
same level that cyclictest reports. The ACTIVATION ID field
serves to relate the *irq* execution to its respective *thread* execution.

The irq/thread splitting is important to clarify at which context
the unexpected high value is coming from. The *irq* context can be
delayed by hardware related actions, such as SMIs, NMIs, IRQs
or by a thread masking interrupts. Once the timer happens, the delay
can also be influenced by blocking caused by threads. For example, by
postponing the scheduler execution via preempt_disable(),  by the
scheduler execution, or by masking interrupts. Threads can
also be delayed by the interference from other threads and IRQs.

The timerlat can also take advantage of the osnoise: traceevents.
For example:

        [root@f32 ~]# cd /sys/kernel/tracing/
        [root@f32 tracing]# echo timerlat > current_tracer
        [root@f32 tracing]# echo osnoise > set_event
        [root@f32 tracing]# echo 25 > osnoise/stop_tracing_total_us
        [root@f32 tracing]# tail -10 trace
             cc1-87882   [005] d..h...   548.771078: #402268 context    irq timer_latency      1585 ns
             cc1-87882   [005] dNLh1..   548.771082: irq_noise: local_timer:236 start 548.771077442 duration 4597 ns
             cc1-87882   [005] dNLh2..   548.771083: irq_noise: reschedule:253 start 548.771083017 duration 56 ns
             cc1-87882   [005] dNLh2..   548.771086: irq_noise: call_function_single:251 start 548.771083811 duration 2048 ns
             cc1-87882   [005] dNLh2..   548.771088: irq_noise: call_function_single:251 start 548.771086814 duration 1495 ns
             cc1-87882   [005] dNLh2..   548.771091: irq_noise: call_function_single:251 start 548.771089194 duration 1558 ns
             cc1-87882   [005] dNLh2..   548.771094: irq_noise: call_function_single:251 start 548.771091719 duration 1932 ns
             cc1-87882   [005] dNLh2..   548.771096: irq_noise: call_function_single:251 start 548.771094696 duration 1050 ns
             cc1-87882   [005] d...3..   548.771101: thread_noise:      cc1:87882 start 548.771078243 duration 10909 ns
      timerlat/5-1035    [005] .......   548.771103: #402268 context thread timer_latency     25960 ns

For further information see: Documentation/trace/timerlat-tracer.rst

Link: https://lkml.kernel.org/r/71f18efc013e1194bcaea1e54db957de2b19ba62.1624372313.git.bristot@redhat.com

Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-06-25 19:57:24 -04:00

404 lines
9.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* This file defines the trace event structures that go into the ring
* buffer directly. They are created via macros so that changes for them
* appear in the format file. Using macros will automate this process.
*
* The macro used to create a ftrace data structure is:
*
* FTRACE_ENTRY( name, struct_name, id, structure, print )
*
* @name: the name used the event name, as well as the name of
* the directory that holds the format file.
*
* @struct_name: the name of the structure that is created.
*
* @id: The event identifier that is used to detect what event
* this is from the ring buffer.
*
* @structure: the structure layout
*
* - __field( type, item )
* This is equivalent to declaring
* type item;
* in the structure.
* - __array( type, item, size )
* This is equivalent to declaring
* type item[size];
* in the structure.
*
* * for structures within structures, the format of the internal
* structure is laid out. This allows the internal structure
* to be deciphered for the format file. Although these macros
* may become out of sync with the internal structure, they
* will create a compile error if it happens. Since the
* internal structures are just tracing helpers, this is not
* an issue.
*
* When an internal structure is used, it should use:
*
* __field_struct( type, item )
*
* instead of __field. This will prevent it from being shown in
* the output file. The fields in the structure should use.
*
* __field_desc( type, container, item )
* __array_desc( type, container, item, len )
*
* type, item and len are the same as __field and __array, but
* container is added. This is the name of the item in
* __field_struct that this is describing.
*
*
* @print: the print format shown to users in the format file.
*/
/*
* Function trace entry - function address and parent function address:
*/
FTRACE_ENTRY_REG(function, ftrace_entry,
TRACE_FN,
F_STRUCT(
__field_fn( unsigned long, ip )
__field_fn( unsigned long, parent_ip )
),
F_printk(" %ps <-- %ps",
(void *)__entry->ip, (void *)__entry->parent_ip),
perf_ftrace_event_register
);
/* Function call entry */
FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
TRACE_GRAPH_ENT,
F_STRUCT(
__field_struct( struct ftrace_graph_ent, graph_ent )
__field_packed( unsigned long, graph_ent, func )
__field_packed( int, graph_ent, depth )
),
F_printk("--> %ps (%d)", (void *)__entry->func, __entry->depth)
);
/* Function return entry */
FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,
F_STRUCT(
__field_struct( struct ftrace_graph_ret, ret )
__field_packed( unsigned long, ret, func )
__field_packed( int, ret, depth )
__field_packed( unsigned int, ret, overrun )
__field_packed( unsigned long long, ret, calltime)
__field_packed( unsigned long long, ret, rettime )
),
F_printk("<-- %ps (%d) (start: %llx end: %llx) over: %d",
(void *)__entry->func, __entry->depth,
__entry->calltime, __entry->rettime,
__entry->depth)
);
/*
* Context switch trace entry - which task (and prio) we switched from/to:
*
* This is used for both wakeup and context switches. We only want
* to create one structure, but we need two outputs for it.
*/
#define FTRACE_CTX_FIELDS \
__field( unsigned int, prev_pid ) \
__field( unsigned int, next_pid ) \
__field( unsigned int, next_cpu ) \
__field( unsigned char, prev_prio ) \
__field( unsigned char, prev_state ) \
__field( unsigned char, next_prio ) \
__field( unsigned char, next_state )
FTRACE_ENTRY(context_switch, ctx_switch_entry,
TRACE_CTX,
F_STRUCT(
FTRACE_CTX_FIELDS
),
F_printk("%u:%u:%u ==> %u:%u:%u [%03u]",
__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
__entry->next_pid, __entry->next_prio, __entry->next_state,
__entry->next_cpu)
);
/*
* FTRACE_ENTRY_DUP only creates the format file, it will not
* create another structure.
*/
FTRACE_ENTRY_DUP(wakeup, ctx_switch_entry,
TRACE_WAKE,
F_STRUCT(
FTRACE_CTX_FIELDS
),
F_printk("%u:%u:%u ==+ %u:%u:%u [%03u]",
__entry->prev_pid, __entry->prev_prio, __entry->prev_state,
__entry->next_pid, __entry->next_prio, __entry->next_state,
__entry->next_cpu)
);
/*
* Stack-trace entry:
*/
#define FTRACE_STACK_ENTRIES 8
FTRACE_ENTRY(kernel_stack, stack_entry,
TRACE_STACK,
F_STRUCT(
__field( int, size )
__array( unsigned long, caller, FTRACE_STACK_ENTRIES )
),
F_printk("\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n",
(void *)__entry->caller[0], (void *)__entry->caller[1],
(void *)__entry->caller[2], (void *)__entry->caller[3],
(void *)__entry->caller[4], (void *)__entry->caller[5],
(void *)__entry->caller[6], (void *)__entry->caller[7])
);
FTRACE_ENTRY(user_stack, userstack_entry,
TRACE_USER_STACK,
F_STRUCT(
__field( unsigned int, tgid )
__array( unsigned long, caller, FTRACE_STACK_ENTRIES )
),
F_printk("\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n\t=> %ps\n"
"\t=> %ps\n\t=> %ps\n",
(void *)__entry->caller[0], (void *)__entry->caller[1],
(void *)__entry->caller[2], (void *)__entry->caller[3],
(void *)__entry->caller[4], (void *)__entry->caller[5],
(void *)__entry->caller[6], (void *)__entry->caller[7])
);
/*
* trace_printk entry:
*/
FTRACE_ENTRY(bprint, bprint_entry,
TRACE_BPRINT,
F_STRUCT(
__field( unsigned long, ip )
__field( const char *, fmt )
__dynamic_array( u32, buf )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->fmt)
);
FTRACE_ENTRY_REG(print, print_entry,
TRACE_PRINT,
F_STRUCT(
__field( unsigned long, ip )
__dynamic_array( char, buf )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->buf),
ftrace_event_register
);
FTRACE_ENTRY(raw_data, raw_data_entry,
TRACE_RAW_DATA,
F_STRUCT(
__field( unsigned int, id )
__dynamic_array( char, buf )
),
F_printk("id:%04x %08x",
__entry->id, (int)__entry->buf[0])
);
FTRACE_ENTRY(bputs, bputs_entry,
TRACE_BPUTS,
F_STRUCT(
__field( unsigned long, ip )
__field( const char *, str )
),
F_printk("%ps: %s",
(void *)__entry->ip, __entry->str)
);
FTRACE_ENTRY(mmiotrace_rw, trace_mmiotrace_rw,
TRACE_MMIO_RW,
F_STRUCT(
__field_struct( struct mmiotrace_rw, rw )
__field_desc( resource_size_t, rw, phys )
__field_desc( unsigned long, rw, value )
__field_desc( unsigned long, rw, pc )
__field_desc( int, rw, map_id )
__field_desc( unsigned char, rw, opcode )
__field_desc( unsigned char, rw, width )
),
F_printk("%lx %lx %lx %d %x %x",
(unsigned long)__entry->phys, __entry->value, __entry->pc,
__entry->map_id, __entry->opcode, __entry->width)
);
FTRACE_ENTRY(mmiotrace_map, trace_mmiotrace_map,
TRACE_MMIO_MAP,
F_STRUCT(
__field_struct( struct mmiotrace_map, map )
__field_desc( resource_size_t, map, phys )
__field_desc( unsigned long, map, virt )
__field_desc( unsigned long, map, len )
__field_desc( int, map, map_id )
__field_desc( unsigned char, map, opcode )
),
F_printk("%lx %lx %lx %d %x",
(unsigned long)__entry->phys, __entry->virt, __entry->len,
__entry->map_id, __entry->opcode)
);
#define TRACE_FUNC_SIZE 30
#define TRACE_FILE_SIZE 20
FTRACE_ENTRY(branch, trace_branch,
TRACE_BRANCH,
F_STRUCT(
__field( unsigned int, line )
__array( char, func, TRACE_FUNC_SIZE+1 )
__array( char, file, TRACE_FILE_SIZE+1 )
__field( char, correct )
__field( char, constant )
),
F_printk("%u:%s:%s (%u)%s",
__entry->line,
__entry->func, __entry->file, __entry->correct,
__entry->constant ? " CONSTANT" : "")
);
FTRACE_ENTRY(hwlat, hwlat_entry,
TRACE_HWLAT,
F_STRUCT(
__field( u64, duration )
__field( u64, outer_duration )
__field( u64, nmi_total_ts )
__field_struct( struct timespec64, timestamp )
__field_desc( s64, timestamp, tv_sec )
__field_desc( long, timestamp, tv_nsec )
__field( unsigned int, nmi_count )
__field( unsigned int, seqnum )
__field( unsigned int, count )
),
F_printk("cnt:%u\tts:%010llu.%010lu\tinner:%llu\touter:%llu\tcount:%d\tnmi-ts:%llu\tnmi-count:%u\n",
__entry->seqnum,
__entry->tv_sec,
__entry->tv_nsec,
__entry->duration,
__entry->outer_duration,
__entry->count,
__entry->nmi_total_ts,
__entry->nmi_count)
);
#define FUNC_REPEATS_GET_DELTA_TS(entry) \
(((u64)(entry)->top_delta_ts << 32) | (entry)->bottom_delta_ts) \
FTRACE_ENTRY(func_repeats, func_repeats_entry,
TRACE_FUNC_REPEATS,
F_STRUCT(
__field( unsigned long, ip )
__field( unsigned long, parent_ip )
__field( u16 , count )
__field( u16 , top_delta_ts )
__field( u32 , bottom_delta_ts )
),
F_printk(" %ps <-%ps\t(repeats:%u delta: -%llu)",
(void *)__entry->ip,
(void *)__entry->parent_ip,
__entry->count,
FUNC_REPEATS_GET_DELTA_TS(__entry))
);
FTRACE_ENTRY(osnoise, osnoise_entry,
TRACE_OSNOISE,
F_STRUCT(
__field( u64, noise )
__field( u64, runtime )
__field( u64, max_sample )
__field( unsigned int, hw_count )
__field( unsigned int, nmi_count )
__field( unsigned int, irq_count )
__field( unsigned int, softirq_count )
__field( unsigned int, thread_count )
),
F_printk("noise:%llu\tmax_sample:%llu\thw:%u\tnmi:%u\tirq:%u\tsoftirq:%u\tthread:%u\n",
__entry->noise,
__entry->max_sample,
__entry->hw_count,
__entry->nmi_count,
__entry->irq_count,
__entry->softirq_count,
__entry->thread_count)
);
FTRACE_ENTRY(timerlat, timerlat_entry,
TRACE_TIMERLAT,
F_STRUCT(
__field( unsigned int, seqnum )
__field( int, context )
__field( u64, timer_latency )
),
F_printk("seq:%u\tcontext:%d\ttimer_latency:%llu\n",
__entry->seqnum,
__entry->context,
__entry->timer_latency)
);