The libtracefs-sqlhist.txt.1 file is generated during the tracefs
library man pages compilation, it should not be part of the sources.
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
Documentation/libtracefs-sqlhist.txt.1 | 351 -------------------------
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-SQLHIST(1)
-==========
-
-NAME
-----
-sqlhist - Tool that uses SQL language to create / show creation of tracefs histograms and synthetic events.
-
-SYNOPSIS
---------
-*sqlhist* ['OPTIONS'] ['SQL-select-command']
-
-DESCRIPTION
------------
-The sqlhist(1) will take an SQL like statement to create tracefs histograms and
-synthetic events that can perform various actions for various handling of the
-data.
-
-The tracefs file system interfaces with the Linux tracing infrastructure that
-has various dynamic and static events through out the kernel. Each of these
-events can have a "histogram" attached to it, where the fields of the event
-will define the buckets of the histogram.
-
-A synthetic event is a way to attach two separate events and use the fields
-and time stamps of those events to create a new dynamic event. This new
-dynamic event is call a synthetic event. The fields of each event can have
-simple calculations done on them where, for example, the delta between
-a field of one event to a field of the other event can be taken. This also
-works for the time stamps of the events where the time delta between the
-two events can also be extracted and placed into the synthetic event.
-
-Other actions can be done from the fields of the events. A snapshot can
-be taken of the kernel ring buffer a variable used in the synthetic
-event creating hits a max, or simply changes.
-
-The commands to create histograms and synthetic events are complex and
-not easy to remember. *sqlhist* is used to convert SQL syntax into the
-commands needed to create the histogram or synthetic event.
-
-The *SQL-select-command* is a SQL string defined by *tracefs_sql*(3).
-
-Note, this must be run as root (or sudo) as interacting with the tracefs
-directory requires root privilege, unless the *-t* option is given with
-a copy of the _tracefs_ directory and its events.
-
-The *sqlhist* is a simple program where its code actual exists in the
-*tracefs_sql*(3) man page.
-
-OPTIONS
--------
-*-n* 'name'::
- The name of the synthetic event to create. This event can then be
- used like any other event, and enabled via *trace-cmd*(1).
-
-*-t* 'tracefs-dir'::
- In order to test this out as non root user, a copy of the tracefs directory
- can be used, and passing that directory with this option will allow
- the program to work. Obviously, *-e* will not work as non-root because
- it will not be able to execute.
-
- # mkdir /tmp/tracing
- # cp -r /sys/kernel/tracing/events /tmp/tracing
- # exit
- $ ./sqlhist -t /tmp/tracing ...
-
-*-e*::
- Not only display the commands to create the histogram, but also execute them.
- This requires root privilege.
-
-*-f* 'file'::
- Instead of reading the SQL commands from the command line, read them from
- _file_. If _file_ is '-' then read from standard input.
-
-*-m* 'var'::
- Do the given action when the variable _var_ hits a new maximum. This can
- not be used with *-c*.
-
-*-c* 'var'::
- Do the given action when the variable _var_ changes its value. This can
- not be used with *-m*.
-
-*-s*::
- Perform a snapshot instead of calling the synthetic event.
-
-*-T*::
- Perform both a snapshot and trace the synthetic event.
-
-*-S* 'fields[,fields]'::
- Save the given fields. The fields must be fields of the "end" event given
- in the *SQL-select-command*
-
-
-EXAMPLES
---------
-
-Create the sqlhist executable:
-
-[source, c]
---
- man tracefs_sql | sed -ne '/^EXAMPLE/,/FILES/ { /EXAMPLE/d ; /FILES/d ; p}' > sqlhist.c
- gcc -o sqlhist sqlhist.c `pkg-config --cflags --libs libtracefs`
---
-
-As described above, for testing purposes, make a copy of the event directory:
-[source, c]
---
- $ mkdir /tmp/tracing
- $ sudo cp -r /sys/kernel/tracing/events /tmp/tracing/
- $ sudo chmod -R 0644 /tmp/tracing/
---
-
-For an example of simple histogram output using the copy of the tracefs directory.
-[source, c]
---
- $ ./sqlhist -t /tmp/tracing/ 'SELECT CAST(call_site as SYM-OFFSET), bytes_req, CAST(bytes_alloc AS _COUNTER_) FROM kmalloc'
---
-
-Produces the output:
-[source, c]
---
- echo 'hist:keys=call_site.sym-offset,bytes_req:vals=bytes_alloc' > /sys/kernel/tracing/events/kmem/kmalloc/trigger
---
-
-Which could be used by root:
-[source, c]
---
- # echo 'hist:keys=call_site.sym-offset,bytes_req:vals=bytes_alloc' > /sys/kernel/tracing/events/kmem/kmalloc/trigger
- # cat /sys/kernel/tracing/events/kmem/kmalloc/hist
-# event histogram
-#
-# trigger info: hist:keys=call_site.sym-offset,bytes_req:vals=hitcount,bytes_alloc:sort=hitcount:size=2048 [active]
-#
-
-{ call_site: [ffffffff813f8d8a] load_elf_phdrs+0x4a/0xb0 , bytes_req: 728 } hitcount: 1 bytes_alloc: 1024
-{ call_site: [ffffffffc0c69e74] nf_ct_ext_add+0xd4/0x1d0 [nf_conntrack] , bytes_req: 128 } hitcount: 1 bytes_alloc: 128
-{ call_site: [ffffffff818355e6] dma_resv_get_fences+0xf6/0x440 , bytes_req: 8 } hitcount: 1 bytes_alloc: 8
-{ call_site: [ffffffffc06dc73f] intel_gt_get_buffer_pool+0x15f/0x290 [i915] , bytes_req: 424 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffff813f8d8a] load_elf_phdrs+0x4a/0xb0 , bytes_req: 616 } hitcount: 1 bytes_alloc: 1024
-{ call_site: [ffffffff8161a44c] __sg_alloc_table+0x11c/0x180 , bytes_req: 32 } hitcount: 1 bytes_alloc: 32
-{ call_site: [ffffffffc070749d] shmem_get_pages+0xad/0x5d0 [i915] , bytes_req: 16 } hitcount: 1 bytes_alloc: 16
-{ call_site: [ffffffffc07507f5] intel_framebuffer_create+0x25/0x60 [i915] , bytes_req: 408 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffffc06fc20f] eb_parse+0x34f/0x910 [i915] , bytes_req: 408 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffffc0700ebd] i915_gem_object_get_pages_internal+0x5d/0x270 [i915] , bytes_req: 16 } hitcount: 1 bytes_alloc: 16
-{ call_site: [ffffffffc0771188] intel_frontbuffer_get+0x38/0x220 [i915] , bytes_req: 400 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffff8161a44c] __sg_alloc_table+0x11c/0x180 , bytes_req: 128 } hitcount: 1 bytes_alloc: 128
-{ call_site: [ffffffff813f8f45] load_elf_binary+0x155/0x1680 , bytes_req: 28 } hitcount: 1 bytes_alloc: 32
-{ call_site: [ffffffffc07038c8] __assign_mmap_offset+0x208/0x3d0 [i915] , bytes_req: 288 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffff813737b2] alloc_bprm+0x32/0x2f0 , bytes_req: 416 } hitcount: 1 bytes_alloc: 512
-{ call_site: [ffffffff813f9027] load_elf_binary+0x237/0x1680 , bytes_req: 64 } hitcount: 1 bytes_alloc: 64
-{ call_site: [ffffffff8161a44c] __sg_alloc_table+0x11c/0x180 , bytes_req: 64 } hitcount: 1 bytes_alloc: 64
-{ call_site: [ffffffffc040ffe7] drm_vma_node_allow+0x27/0xe0 [drm] , bytes_req: 40 } hitcount: 2 bytes_alloc: 128
-{ call_site: [ffffffff813cda98] __do_sys_timerfd_create+0x58/0x1c0 , bytes_req: 336 } hitcount: 2 bytes_alloc: 1024
-{ call_site: [ffffffff818355e6] dma_resv_get_fences+0xf6/0x440 , bytes_req: 40 } hitcount: 2 bytes_alloc: 128
-{ call_site: [ffffffff8139b75a] single_open+0x2a/0xa0 , bytes_req: 32 } hitcount: 2 bytes_alloc: 64
-{ call_site: [ffffffff815df715] bio_kmalloc+0x25/0x80 , bytes_req: 136 } hitcount: 2 bytes_alloc: 384
-{ call_site: [ffffffffc071e5cd] i915_vma_work+0x1d/0x50 [i915] , bytes_req: 416 } hitcount: 3 bytes_alloc: 1536
-{ call_site: [ffffffff81390d0d] alloc_fdtable+0x4d/0x100 , bytes_req: 56 } hitcount: 3 bytes_alloc: 192
-{ call_site: [ffffffffc06ff65f] i915_gem_do_execbuffer+0x158f/0x2440 [i915] , bytes_req: 16 } hitcount: 4 bytes_alloc: 64
-{ call_site: [ffffffff8137713c] alloc_pipe_info+0x5c/0x230 , bytes_req: 384 } hitcount: 5 bytes_alloc: 2560
-{ call_site: [ffffffff813771b4] alloc_pipe_info+0xd4/0x230 , bytes_req: 640 } hitcount: 5 bytes_alloc: 5120
-{ call_site: [ffffffff81834cdb] dma_resv_list_alloc+0x1b/0x40 , bytes_req: 40 } hitcount: 6 bytes_alloc: 384
-{ call_site: [ffffffff81834cdb] dma_resv_list_alloc+0x1b/0x40 , bytes_req: 56 } hitcount: 9 bytes_alloc: 576
-{ call_site: [ffffffff8120086e] tracing_map_sort_entries+0x9e/0x3e0 , bytes_req: 24 } hitcount: 60 bytes_alloc: 1920
-
-Totals:
- Hits: 122
- Entries: 30
- Dropped: 0
---
-
-Note, although the examples use uppercase for the SQL keywords, they do not have
-to be. 'SELECT' could also be 'select' or even 'sElEcT'.
-
-By using the full SQL language, synthetic events can be made and processed.
-For example, using *sqlhist* along with *trace-cmd*(1), wake up latency can
-be recorded by creating a synthetic event by attaching the _sched_waking_
-and the _sched_switch_ events.
-
-[source, c]
---
- # sqlhist -n wakeup_lat -e -T -m lat 'SELECT end.next_comm AS comm, (end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) AS lat FROM ' \
- 'sched_waking AS start JOIN sched_switch AS end ON start.pid = end.next_pid WHERE end.next_prio < 100 && end.next_comm == "cyclictest"'
- # trace-cmd start -e all -e wakeup_lat -R stacktrace
- # cyclictest -l 1000 -p80 -i250 -a -t -q -m -d 0 -b 1000 --tracemark
- # trace-cmd show -s | tail -30
- <idle>-0 [002] dNh4 23454.902246: sched_wakeup: comm=cyclictest pid=12272 prio=120 target_cpu=002
- <idle>-0 [005] ...1 23454.902246: cpu_idle: state=4294967295 cpu_id=5
- <idle>-0 [007] d..1 23454.902246: cpu_idle: state=0 cpu_id=7
- <idle>-0 [002] dNh1 23454.902247: hrtimer_expire_exit: hrtimer=0000000037956dc2
- <idle>-0 [005] d..1 23454.902248: cpu_idle: state=0 cpu_id=5
- <idle>-0 [002] dNh1 23454.902248: write_msr: 6e0, value 4866ce957272
- <idle>-0 [006] ...1 23454.902248: cpu_idle: state=4294967295 cpu_id=6
- <idle>-0 [002] dNh1 23454.902249: local_timer_exit: vector=236
- <idle>-0 [006] d..1 23454.902250: cpu_idle: state=0 cpu_id=6
- <idle>-0 [002] .N.1 23454.902250: cpu_idle: state=4294967295 cpu_id=2
- <idle>-0 [002] dN.1 23454.902251: rcu_utilization: Start context switch
- <idle>-0 [002] dN.1 23454.902252: rcu_utilization: End context switch
- <idle>-0 [001] ...1 23454.902252: cpu_idle: state=4294967295 cpu_id=1
- <idle>-0 [002] dN.3 23454.902253: prandom_u32: ret=3692516021
- <idle>-0 [001] d..1 23454.902254: cpu_idle: state=0 cpu_id=1
- <idle>-0 [002] d..2 23454.902254: sched_switch: prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=cyclictest next_pid=12275 next_prio=19
- <idle>-0 [002] d..4 23454.902256: wakeup_lat: next_comm=cyclictest lat=17
- <idle>-0 [002] d..5 23454.902258: <stack trace>
- => trace_event_raw_event_synth
- => action_trace
- => event_hist_trigger
- => event_triggers_call
- => trace_event_buffer_commit
- => trace_event_raw_event_sched_switch
- => __traceiter_sched_switch
- => __schedule
- => schedule_idle
- => do_idle
- => cpu_startup_entry
- => secondary_startup_64_no_verify
---
-
-Here's the options for *sqlhist* explained:
-
- *-n wakeup_lat* ::
- Name the synthetic event to use *wakeup_lat*.
-
- *-e*::
- Execute the commands that are printed.
-
- *-T*::
- Perform both a trace action and then a snapshot action (swap the buffer into the static 'snapshot' buffer).
-
- *-m lat*::
- Trigger the actions whenever 'lat' hits a new maximum value.
-
-Now a breakdown of the SQL statement:
-[source, c]
---
- 'SELECT end.next_comm AS comm, (end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) AS lat FROM ' \
- 'sched_waking AS start JOIN sched_switch AS end ON start.pid = end.next_pid WHERE end.next_prio < 100 && end.next_comm == "cyclictest"'
---
- *end.next_comm AS comm*::
- Save the 'sched_switch' field *next_comm* and place it into the *comm* field of the 'wakeup_lat' synthetic event.
-
- *(end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) AS lat*::
- Take the delta of the time stamps from the 'sched_switch' event and the 'sched_waking' event.
- As time stamps are usually recorded in nanoseconds, *TIMESTAMP* would give the full nanosecond time stamp,
- but here, the *TIMESTAMP_USECS* will truncate it into microseconds. The value is saved in the
- variable *lat*, which will also be recorded in the synthetic event.
-
- *FROM 'sched_waking' AS start JOIN sched_switch AS end ON start.pid = end.next_pid*::
- Create the synthetic event by joining _sched_waking_ to _sched_switch_, matching
- the _sched_waking_ 'pid' field with the _sched_switch_ 'next_pid' field.
- Also make *start* an alias for _sched_waking_ and *end* an alias for _sched_switch_
- which then an use *start* and *end* as a subsitute for _sched_waking_ and _sched_switch_
- respectively through out the rest of the SQL statement.
-
- *WHERE end.next_prio < 100 && end.next_comm == "cyclictest"*::
- Filter the logic where it executes only if _sched_waking_ 'next_prio' field
- is less than 100. (Note, in the Kernel, priorities are inverse, and the real-time
- priorities are represented from 0-100 where 0 is the highest priority).
- Also only trace when the 'next_comm' (the task scheduling in) of the _sched_switch_
- event has the name "cyclictest".
-
-For the *trace-cmd*(3) command:
-[source, c]
---
- trace-cmd start -e all -e wakeup_lat -R stacktrace
---
-
- *trace-cmd start*::
- Enables tracing (does not record to a file).
-
- *-e all*::
- Enable all events
-
- *-e wakeup_lat -R stacktrace*::
- have the "wakeup_lat" event (our synthetic event) enable the *stacktrace* trigger, were
- for every instance of the "wakeup_lat" event, a kernel stack trace will be recorded
- in the ring buffer.
-
-After calling *cyclictest* (a real-time tool to measure wakeup latency), read the snapshot
-buffer.
-
- *trace-cmd show -s*::
- *trace-cmd show* reads the kernel ring buffer, and the *-s* option will read the *snapshot*
- buffer instead of the normal one.
-
-[source, c]
---
- <idle>-0 [002] d..4 23454.902256: wakeup_lat: next_comm=cyclictest lat=17
---
- We see on the "wakeup_lat" event happened on CPU 2, with a wake up latency 17 microseconds.
-
-This can be extracted into a *trace.dat* file that *trace-cmd*(3) can read and do further
-analysis, as well as *kernelshark*.
-
-[source, c]
---
- # trace-cmd extract -s
- # trace-cmd report --cpu 2 | tail -30
- <idle>-0 [002] 23454.902238: prandom_u32: ret=1633425088
- <idle>-0 [002] 23454.902239: sched_wakeup: cyclictest:12275 [19] CPU:002
- <idle>-0 [002] 23454.902241: hrtimer_expire_exit: hrtimer=0xffffbbd68286fe60
- <idle>-0 [002] 23454.902241: hrtimer_cancel: hrtimer=0xffffbbd6826efe70
- <idle>-0 [002] 23454.902242: hrtimer_expire_entry: hrtimer=0xffffbbd6826efe70 now=23455294430750 function=hrtimer_wakeup/0x0
- <idle>-0 [002] 23454.902243: sched_waking: comm=cyclictest pid=12272 prio=120 target_cpu=002
- <idle>-0 [002] 23454.902244: prandom_u32: ret=1102749734
- <idle>-0 [002] 23454.902246: sched_wakeup: cyclictest:12272 [120] CPU:002
- <idle>-0 [002] 23454.902247: hrtimer_expire_exit: hrtimer=0xffffbbd6826efe70
- <idle>-0 [002] 23454.902248: write_msr: 6e0, value 4866ce957272
- <idle>-0 [002] 23454.902249: local_timer_exit: vector=236
- <idle>-0 [002] 23454.902250: cpu_idle: state=4294967295 cpu_id=2
- <idle>-0 [002] 23454.902251: rcu_utilization: Start context switch
- <idle>-0 [002] 23454.902252: rcu_utilization: End context switch
- <idle>-0 [002] 23454.902253: prandom_u32: ret=3692516021
- <idle>-0 [002] 23454.902254: sched_switch: swapper/2:0 [120] R ==> cyclictest:12275 [19]
- <idle>-0 [002] 23454.902256: wakeup_lat: next_comm=cyclictest lat=17
- <idle>-0 [002] 23454.902258: kernel_stack: <stack trace >
-=> trace_event_raw_event_synth (ffffffff8121a0db)
-=> action_trace (ffffffff8121e9fb)
-=> event_hist_trigger (ffffffff8121ca8d)
-=> event_triggers_call (ffffffff81216c72)
-=> trace_event_buffer_commit (ffffffff811f7618)
-=> trace_event_raw_event_sched_switch (ffffffff8110fda4)
-=> __traceiter_sched_switch (ffffffff8110d449)
-=> __schedule (ffffffff81c02002)
-=> schedule_idle (ffffffff81c02c86)
-=> do_idle (ffffffff8111e898)
-=> cpu_startup_entry (ffffffff8111eba9)
-=> secondary_startup_64_no_verify (ffffffff81000107)
---
-
-BUGS
-----
-
-As *sqlhist* is just example code from a man page, it is guaranteed to contain
-lots of bugs. For one thing, not all error paths are covered properly.
-
-SEE ALSO
---------
-trace-cmd(1), tracefs_sql(3)
-
-AUTHOR
-------
-Written by Steven Rostedt, <rostedt@xxxxxxxxxxx>
-
-RESOURCES
----------
-https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/
-
-COPYING
--------
-Copyright \(C) 2021 , Inc. Free use of this software is granted under
-the terms of the GNU Public License (GPL).
-
--
2.31.1
|