TRACE\-CMD\-REPORTSection: [FIXME: manual] (1)
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NAMEtrace-cmd-report - show in ASCII a trace created by trace-cmd record
The trace-cmd(1) report command will output a human readable report of a trace created by trace-cmd record.
- By default, trace-cmd report will read the file trace.dat. But the -i option open up the given input-file instead. Note, the input file may also be specified as the last item on the command line.
- This outputs the endianess of the file. trace-cmd report is smart enough to be able to read big endian files on little endian machines, and vise versa.
- This outputs the list of functions that have been recorded in the file.
- This outputs the list of "trace_printk()" data. The raw trace data points to static pointers in the kernel. This must be stored in the trace.dat file.
- This lists the possible events in the file (but this list is not necessarily the list of events in the file).
- This will list the event formats that are stored in the trace.dat file.
- Add a filter to limit what events are displayed. The format of the filter is:
<events> ':' <filter> <events> = SYSTEM'/'EVENT | SYSTEM | EVENT | <events> ',' <events> <filter> = EVENT_FIELD <op> <value> | <filter> '&&' <filter> | <filter> '||' <filter> | '(' <filter> ')' | '!' <filter> <op> = '==' | '!=' | '>=' | '<=' | '>' | '<' | '&' | '|' | '^' | '+' | '-' | '*' | '/' | '%' <value> = NUM | STRING | EVENT_FIELD
SYSTEM is the name of the system to filter on. If the EVENT is left out, then it applies to all events under the SYSTEM. If only one string is used without the '/' to deliminate between SYSTEM and EVENT, then the filter will be applied to all systems and events that match the given string.
Whitespace is ignored, such that "sched:next_pid==123" is equivalent to "sched : next_pid == 123".
STRING is defined with single or double quotes (single quote must end with single quote, and double with double). Whitespace within quotes are not ignored.
The representation of a SYSTEM or EVENT may also be a regular expression as defined by 'regcomp(3)'.
The EVENT_FIELD is the name of the field of an event that is being filtered. If the event does not contain the EVENT_FIELD, that part of the equation will be considered false.
-F 'sched : bogus == 1 || common_pid == 2'
The "bogus == 1" will always evaluate to FALSE because no event has a field called "bogus", but the "common_pid == 2" will still be evaluated since all events have the field "common_pid". Any "sched" event that was traced by the process with the PID of 2 will be shown.
Note, the EVENT_FIELD is the field name as shown by an events format (as displayed with *--events*), and not what is found in the output. If the output shows "ID:foo" but the field that "foo" belongs to was called "name" in the event format, then "name" must be used in the filter. The same is true about values. If the value that is displayed is converted by to a string symbol, the filter checks the original value and not the value displayed. For example, to filter on all tasks that were in the running state at a context switch:
-F 'sched/sched_switch : prev_state==0'
Although the output displays 'R', having 'prev_stat=="R"' will not work.
- This causes the following filters of -F to filter out the matching events.
-v -F 'sched/sched_switch : prev_state == 0'
Will not display any sched_switch events that have a prev_state of 0. Removing the *-v* will only print out those events.
- Show the plugins that are loaded.
- This will not load system wide plugins. It loads "local only". That is what it finds in the ~/.trace-cmd/plugins directory.
- This will not load any plugins.
- This will show the events in "raw" format. That is, it will ignore the eventcqs print formatting and just print the contents of each field.
- This adds a "latency output" format. Information about interrupts being disabled, soft irq being disabled, the "need_resched" flag being set, preempt count, and big kernel lock are all being recorded with every event. But the default display does not show this information. This option will set display this information with 6 characters. When one of the fields is zero or N/A a '.\' is shown.
<idle>-0 0d.h1. 106467.859747: function: ktime_get <-- tick_check_idle
The 0d.h1. denotes this information. The first character is never a '.' and represents what CPU the trace was recorded on (CPU 0). The 'd' denotes that interrupts were disabled. The 'h' means that this was called inside an interrupt handler. The '1' is the preemption disabled (preempt_count) was set to one. The two '.'s are "need_resched" flag and kernel lock counter. If the "need_resched" flag is set, then that character would be a 'N'.
- If both the sched_switch and sched_wakeup events are enabled, then this option will report the latency between the time the task was first woken, and the time it was scheduled in.
- Quiet non critical warnings.
Using a trace.dat file that was created with:
# trace-cmd record -p function -e all sleep 5
The default report shows:
# trace-cmd report trace-cmd-16129  158126.498411: function: __mutex_unlock_slowpath <-- mutex_unlock trace-cmd-16131  158126.498411: kmem_cache_alloc: call_site=811223c5 ptr=0xffff88003ecf2b40 bytes_req=272 bytes_alloc=320 gfp_flags=GFP_KERNEL|GFP_ZERO trace-cmd-16130  158126.498411: function: do_splice_to <-- sys_splice sleep-16133  158126.498412: function: inotify_inode_queue_event <-- vfs_write trace-cmd-16129  158126.498420: lock_release: 0xffff88003f1fa4f8 &sb->s_type->i_mutex_key trace-cmd-16131  158126.498421: function: security_file_alloc <-- get_empty_filp sleep-16133  158126.498422: function: __fsnotify_parent <-- vfs_write trace-cmd-16130  158126.498422: function: rw_verify_area <-- do_splice_to trace-cmd-16131  158126.498424: function: cap_file_alloc_security <-- security_file_alloc trace-cmd-16129  158126.498425: function: syscall_trace_leave <-- int_check_syscall_exit_work sleep-16133  158126.498426: function: inotify_dentry_parent_queue_event <-- vfs_write trace-cmd-16130  158126.498426: function: security_file_permission <-- rw_verify_area trace-cmd-16129  158126.498428: function: audit_syscall_exit <-- syscall_trace_leave [...]
To see everything but the function traces:
# trace-cmd report -v -F 'function' trace-cmd-16131  158126.498411: kmem_cache_alloc: call_site=811223c5 ptr=0xffff88003ecf2b40 bytes_req=272 bytes_alloc=320 gfp_flags=GFP_KERNEL|GFP_ZERO trace-cmd-16129  158126.498420: lock_release: 0xffff88003f1fa4f8 &sb->s_type->i_mutex_key trace-cmd-16130  158126.498436: lock_acquire: 0xffffffff8166bf78 read all_cpu_access_lock trace-cmd-16131  158126.498438: lock_acquire: 0xffff88003df5b520 read &fs->lock trace-cmd-16129  158126.498446: kfree: call_site=810a7abb ptr=0x0 trace-cmd-16130  158126.498448: lock_acquire: 0xffff880002250a80 &per_cpu(cpu_access_lock, cpu) trace-cmd-16129  158126.498450: sys_exit_splice: 0xfffffff5 trace-cmd-16131  158126.498454: lock_release: 0xffff88003df5b520 &fs->lock sleep-16133  158126.498456: kfree: call_site=810a7abb ptr=0x0 sleep-16133  158126.498460: sys_exit_write: 0x1 trace-cmd-16130  158126.498462: kmalloc: call_site=810bf95b ptr=0xffff88003dedc040 bytes_req=24 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO
To see only the kmalloc calls that were greater than 1000 bytes:
#trace-cmd report -F 'kmalloc: bytes_req > 1000' <idle>-0  158128.126641: kmalloc: call_site=81330635 ptr=0xffff88003c2fd000 bytes_req=2096 bytes_alloc=4096 gfp_flags=GFP_ATOMIC
To see wakeups and sched switches that left the previous task in the running state:
# trace-cmd report -F 'sched: prev_state == 0 || (success == 1)' trace-cmd-16132  158126.499951: sched_wakeup: comm=trace-cmd pid=16129 prio=120 success=1 target_cpu=002 trace-cmd-16132  158126.500401: sched_switch: prev_comm=trace-cmd prev_pid=16132 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=16129 next_prio=120 <idle>-0  158126.500585: sched_wakeup: comm=trace-cmd pid=16130 prio=120 success=1 target_cpu=003 <idle>-0  158126.501241: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=16130 next_prio=120 trace-cmd-16132  158126.502475: sched_wakeup: comm=trace-cmd pid=16131 prio=120 success=1 target_cpu=000 trace-cmd-16131  158126.506516: sched_wakeup: comm=trace-cmd pid=16129 prio=120 success=1 target_cpu=002 <idle>-0  158126.550110: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=16130 next_prio=120 trace-cmd-16131  158126.570243: sched_wakeup: comm=trace-cmd pid=16129 prio=120 success=1 target_cpu=003 trace-cmd-16130  158126.618202: sched_switch: prev_comm=trace-cmd prev_pid=16130 prev_prio=120 prev_state=R ==> next_comm=yum-updatesd next_pid=3088 next_prio=1 20 trace-cmd-16129  158126.622379: sched_wakeup: comm=trace-cmd pid=16131 prio=120 success=1 target_cpu=003 trace-cmd-16129  158126.649287: sched_wakeup: comm=trace-cmd pid=16131 prio=120 success=1 target_cpu=000
The above needs a little explanation. The filter specifies the "sched" subsystem, which includes both sched_switch and sched_wakeup events. Any event that does not have the format field "prev_state" or "success", will evaluate those expressions as FALSE, and will not produce a match. Using "||" will have the "prev_state" test happen for the "sched_switch" event and the "success" test happen for the "sched_wakeup" event.
# trace-cmd report -w -F 'sched_switch, sched_wakeup.*' [...] trace-cmd-16130  158131.580616: sched_wakeup: comm=trace-cmd pid=16131 prio=120 success=1 target_cpu=003 trace-cmd-16129  158131.581502: sched_switch: prev_comm=trace-cmd prev_pid=16129 prev_prio=120 prev_state=S ==> next_comm=trace-cmd next_pid=16131 next_prio=120 Latency: 885.901 usecs trace-cmd-16131  158131.582414: sched_wakeup: comm=trace-cmd pid=16129 prio=120 success=1 target_cpu=000 trace-cmd-16132  158131.583219: sched_switch: prev_comm=trace-cmd prev_pid=16132 prev_prio=120 prev_state=S ==> next_comm=trace-cmd next_pid=16129 next_prio=120 Latency: 804.809 usecs sleep-16133  158131.584121: sched_wakeup: comm=trace-cmd pid=16120 prio=120 success=1 target_cpu=002 trace-cmd-16129  158131.584128: sched_wakeup: comm=trace-cmd pid=16132 prio=120 success=1 target_cpu=001 sleep-16133  158131.584275: sched_switch: prev_comm=sleep prev_pid=16133 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=16120 next_prio=120 Latency: 153.915 usecs trace-cmd-16130  158131.585284: sched_switch: prev_comm=trace-cmd prev_pid=16130 prev_prio=120 prev_state=S ==> next_comm=trace-cmd next_pid=16132 next_prio=120 Latency: 1155.677 usecs Average wakeup latency: 26626.656 usecs
The above trace produces the wakeup latencies of the tasks. The "sched_switch" event reports each individual latency after writing the event information. At the end of the report, the average wakeup latency is reported.
# trace-cmd report -w -F 'sched_switch, sched_wakeup.*: prio < 100 || next_prio < 100' <idle>-0  158131.516753: sched_wakeup: comm=ksoftirqd/3 pid=13 prio=49 success=1 target_cpu=003 <idle>-0  158131.516855: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=ksoftirqd/3 next_pid=13 next_prio=49 Latency: 101.244 usecs <idle>-0  158131.533781: sched_wakeup: comm=ksoftirqd/3 pid=13 prio=49 success=1 target_cpu=003 <idle>-0  158131.533897: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=ksoftirqd/3 next_pid=13 next_prio=49 Latency: 115.608 usecs <idle>-0  158131.569730: sched_wakeup: comm=ksoftirqd/3 pid=13 prio=49 success=1 target_cpu=003 <idle>-0  158131.569851: sched_switch: prev_comm=swapper prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=ksoftirqd/3 next_pid=13 next_prio=49 Latency: 121.024 usecs Average wakeup latency: 110.021 usecs
The above version will only show the wakeups and context switches of Real Time tasks. The prio used inside the kernel starts at 0 for highest priority. That is prio 0 is equivalent to user space real time priority 99, and priority 98 is equivalent to user space real time priority 1. Prios less than 100 represent Real Time tasks.
Written by Steven Rostedt, <m[blue]firstname.lastname@example.org>
This document was created by man2html, using the manual pages.
Time: 05:29:11 GMT, December 24, 2015