1 ====================
2 rtla-timerlat-top
3 ====================
4 -------------------------------------------
5 Measures the operating system timer latency
6 -------------------------------------------
7
8 :Manual section: 1
9
10 SYNOPSIS
11 ========
12 **rtla timerlat top** [*OPTIONS*] ...
13
14 DESCRIPTION
15 ===========
16
17 .. include:: common_timerlat_description.rst
18
19 The **rtla timerlat top** displays a summary o
20 from the *timerlat* tracer. It also provides i
21 operating system noise via the **osnoise:** tr
22 seem with the option **-T**.
23
24 OPTIONS
25 =======
26
27 .. include:: common_timerlat_options.rst
28
29 .. include:: common_top_options.rst
30
31 .. include:: common_options.rst
32
33 .. include:: common_timerlat_aa.rst
34
35 **--aa-only** *us*
36
37 Set stop tracing conditions and run wi
38 Print the auto-analysis if the system
39 is useful to reduce rtla timerlat CPU,
40 collecting the statistics.
41
42 EXAMPLE
43 =======
44
45 In the example below, the timerlat tracer is d
46 automatic trace mode, instructing the tracer t
47 higher is found::
48
49 # timerlat -a 40 -c 1-23 -q
50 Timer Lat
51 0 00:00:12 | IRQ Timer Latency
52 CPU COUNT | cur min av
53 1 #12322 | 0 0
54 2 #12322 | 3 0
55 3 #12322 | 1 0
56 4 #12322 | 1 0
57 5 #12322 | 0 0
58 6 #12322 | 1 0
59 7 #12322 | 0 0
60 8 #12322 | 1 0
61 9 #12322 | 0 0
62 10 #12322 | 1 0
63 11 #12322 | 0 0
64 12 #12321 | 1 0
65 13 #12319 | 0 0
66 14 #12321 | 1 0
67 15 #12321 | 1 0
68 16 #12318 | 0 0
69 17 #12319 | 0 0
70 18 #12318 | 0 0
71 19 #12319 | 0 0
72 20 #12317 | 0 0
73 21 #12318 | 0 0
74 22 #12319 | 0 0
75 23 #12320 | 28 0
76 rtla timerlat hit stop tracing
77 ## CPU 23 hit stop tracing, analyzing it ##
78 IRQ handler delay:
79 IRQ latency:
80 Timerlat IRQ duration:
81 Blocking thread:
82 objtool:49256
83 Blocking thread stacktrace
84 -> timerlat_irq
85 -> __hrtimer_run_queues
86 -> hrtimer_interrupt
87 -> __sysvec_apic_timer_interru
88 -> sysvec_apic_timer_interrupt
89 -> asm_sysvec_apic_timer_inter
90 -> _raw_spin_unlock_irqrestore
91 -> cgroup_rstat_flush_locked
92 -> cgroup_rstat_flush_irqsafe
93 -> mem_cgroup_flush_stats
94 -> mem_cgroup_wb_stats
95 -> balance_dirty_pages
96 -> balance_dirty_pages_ratelim
97 -> btrfs_buffered_write
98 -> btrfs_do_write_iter
99 -> vfs_write
100 -> __x64_sys_pwrite64
101 -> do_syscall_64
102 -> entry_SYSCALL_64_after_hwfr
103 --------------------------------------------
104 Thread latency:
105
106 The system has exit from idle latency!
107 Max timerlat IRQ latency from idle: 17.48
108 Saving trace to timerlat_trace.txt
109
110 In this case, the major factor was the delay s
111 that handles **timerlat** wakeup: *65.52%*. Th
112 current thread masking interrupts, which can b
113 thread stacktrace: the current thread (*objtoo
114 via *raw spin lock* operations inside mem cgro
115 syscall in a btrfs file system.
116
117 The raw trace is saved in the **timerlat_trace
118
119 Note that **rtla timerlat** was dispatched wit
120 threads' priority. That is generally not neede
121 priority *FIFO:95* by default, which is a comm
122 kernel developers to analyze scheduling delays
123
124 SEE ALSO
125 --------
126 **rtla-timerlat**\(1), **rtla-timerlat-hist**\
127
128 *timerlat* tracer documentation: <https://www.
129
130 AUTHOR
131 ------
132 Written by Daniel Bristot de Oliveira <bristot@
133
134 .. include:: common_appendix.rst
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