tree: git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace trace/for-next
head: 9f712417e1fc7d3db042941524e59573e02a55c7
commit: 88238513bb26713ef6d4418bdf1af062fe608bcb [19/23] tracing/histogram: Document variable stacktrace
reproduce:
# https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git/commit/?id=88238513bb26713ef6d4418bdf1af062fe608bcb
git remote add trace git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
git fetch --no-tags trace trace/for-next
git checkout 88238513bb26713ef6d4418bdf1af062fe608bcb
make menuconfig
# enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
make htmldocs
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
All warnings (new ones prefixed by >>):
>> Documentation/trace/histogram.rst:1969: WARNING: Unexpected indentation.
>> Documentation/trace/histogram.rst:1970: WARNING: Block quote ends without a blank line; unexpected unindent.
>> Documentation/trace/histogram.rst:2014: WARNING: Definition list ends without a blank line; unexpected unindent.
vim +1969 Documentation/trace/histogram.rst
1949
1950 # cd /sys/kernel/tracing
1951 # echo 's:block_lat pid_t pid; u64 delta; unsigned long[] stack;' > dynamic_events
1952 # echo 'hist:keys=next_pid:ts=common_timestamp.usecs,st=stacktrace if prev_state == 2' >> events/sched/sched_switch/trigger
1953 # echo 'hist:keys=prev_pid:delta=common_timestamp.usecs-$ts,s=$st:onmax($delta).trace(block_lat,prev_pid,$delta,$s)' >> events/sched/sched_switch/trigger
1954 # echo 1 > events/synthetic/block_lat/enable
1955 # cat trace
1956
1957 # tracer: nop
1958 #
1959 # entries-in-buffer/entries-written: 2/2 #P:8
1960 #
1961 # _-----=> irqs-off/BH-disabled
1962 # / _----=> need-resched
1963 # | / _---=> hardirq/softirq
1964 # || / _--=> preempt-depth
1965 # ||| / _-=> migrate-disable
1966 # |||| / delay
1967 # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
1968 # | | | ||||| | |
> 1969 <idle>-0 [005] d..4. 521.164922: block_lat: pid=0 delta=8322 stack=STACK:
> 1970 => __schedule+0x448/0x7b0
1971 => schedule+0x5a/0xb0
1972 => io_schedule+0x42/0x70
1973 => bit_wait_io+0xd/0x60
1974 => __wait_on_bit+0x4b/0x140
1975 => out_of_line_wait_on_bit+0x91/0xb0
1976 => jbd2_journal_commit_transaction+0x1679/0x1a70
1977 => kjournald2+0xa9/0x280
1978 => kthread+0xe9/0x110
1979 => ret_from_fork+0x2c/0x50
1980
1981 <...>-2 [004] d..4. 525.184257: block_lat: pid=2 delta=76 stack=STACK:
1982 => __schedule+0x448/0x7b0
1983 => schedule+0x5a/0xb0
1984 => schedule_timeout+0x11a/0x150
1985 => wait_for_completion_killable+0x144/0x1f0
1986 => __kthread_create_on_node+0xe7/0x1e0
1987 => kthread_create_on_node+0x51/0x70
1988 => create_worker+0xcc/0x1a0
1989 => worker_thread+0x2ad/0x380
1990 => kthread+0xe9/0x110
1991 => ret_from_fork+0x2c/0x50
1992
1993 A synthetic event that has a stacktrace field may use it as a key in histogram:
1994
1995 # echo 'hist:delta.buckets=100,stack.stacktrace:sort=delta' > events/synthetic/block_lat/trigger
1996 # cat events/synthetic/block_lat/hist
1997
1998 # event histogram
1999 #
2000 # trigger info: hist:keys=delta.buckets=100,stacktrace:vals=hitcount:sort=delta.buckets=100:size=2048 [active]
2001 #
2002
2003 { delta: ~ 0-99, stacktrace:
2004 event_hist_trigger+0x464/0x480
2005 event_triggers_call+0x52/0xe0
2006 trace_event_buffer_commit+0x193/0x250
2007 trace_event_raw_event_sched_switch+0xfc/0x150
2008 __traceiter_sched_switch+0x41/0x60
2009 __schedule+0x448/0x7b0
2010 schedule_idle+0x26/0x40
2011 cpu_startup_entry+0x19/0x20
2012 start_secondary+0xed/0xf0
2013 secondary_startup_64_no_verify+0xe0/0xeb
> 2014 } hitcount: 6
2015 { delta: ~ 0-99, stacktrace:
2016 event_hist_trigger+0x464/0x480
2017 event_triggers_call+0x52/0xe0
2018 trace_event_buffer_commit+0x193/0x250
2019 trace_event_raw_event_sched_switch+0xfc/0x150
2020 __traceiter_sched_switch+0x41/0x60
2021 __schedule+0x448/0x7b0
2022 schedule_idle+0x26/0x40
2023 cpu_startup_entry+0x19/0x20
2024 __pfx_kernel_init+0x0/0x10
2025 arch_call_rest_init+0xa/0x24
2026 start_kernel+0x964/0x98d
2027 secondary_startup_64_no_verify+0xe0/0xeb
2028 } hitcount: 3
2029 { delta: ~ 0-99, stacktrace:
2030 event_hist_trigger+0x464/0x480
2031 event_triggers_call+0x52/0xe0
2032 trace_event_buffer_commit+0x193/0x250
2033 trace_event_raw_event_sched_switch+0xfc/0x150
2034 __traceiter_sched_switch+0x41/0x60
2035 __schedule+0x448/0x7b0
2036 schedule+0x5a/0xb0
2037 worker_thread+0xaf/0x380
2038 kthread+0xe9/0x110
2039 ret_from_fork+0x2c/0x50
2040 } hitcount: 1
2041 { delta: ~ 100-199, stacktrace:
2042 event_hist_trigger+0x464/0x480
2043 event_triggers_call+0x52/0xe0
2044 trace_event_buffer_commit+0x193/0x250
2045 trace_event_raw_event_sched_switch+0xfc/0x150
2046 __traceiter_sched_switch+0x41/0x60
2047 __schedule+0x448/0x7b0
2048 schedule_idle+0x26/0x40
2049 cpu_startup_entry+0x19/0x20
2050 start_secondary+0xed/0xf0
2051 secondary_startup_64_no_verify+0xe0/0xeb
2052 } hitcount: 15
2053 [..]
2054 { delta: ~ 8500-8599, stacktrace:
2055 event_hist_trigger+0x464/0x480
2056 event_triggers_call+0x52/0xe0
2057 trace_event_buffer_commit+0x193/0x250
2058 trace_event_raw_event_sched_switch+0xfc/0x150
2059 __traceiter_sched_switch+0x41/0x60
2060 __schedule+0x448/0x7b0
2061 schedule_idle+0x26/0x40
2062 cpu_startup_entry+0x19/0x20
2063 start_secondary+0xed/0xf0
2064 secondary_startup_64_no_verify+0xe0/0xeb
2065 } hitcount: 1
2066
2067 Totals:
2068 Hits: 89
2069 Entries: 11
2070 Dropped: 0
2071
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