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linux/kernel/trace
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Steven Rostedt (Google) 0a6d7d4541 ftrace: Be more specific about arch impact when function tracer is enabled 
It was brought up that on ARMv7, that because the FUNCTION_TRACER does not
use nops to keep function tracing disabled because of the use of a link
register, it does have some performance impact.

The start of functions when -pg is used to compile the kernel is:

	push    {lr}
	bl      8010e7c0 <__gnu_mcount_nc>

When function tracing is tuned off, it becomes:

	push    {lr}
	add   sp, sp, #4

Which just puts the stack back to its normal location. But these two
instructions at the start of every function does incur some overhead.

Be more honest in the Kconfig FUNCTION_TRACER description and specify that
the overhead being in the noise was x86 specific, but other architectures
may vary.

Link: https://lore.kernel.org/all/20220705105416.GE5208@pengutronix.de/
Link: https://lkml.kernel.org/r/20220706161231.085a83da@gandalf.local.home

Reported-by: Sascha Hauer <sha@pengutronix.de>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2022-07-12 16:36:34 -04:00
..
blktrace.c block: serialize all debugfs operations using q->debugfs_mutex 2022-06-17 07:31:05 -06:00
bpf_trace.c bpf: Force cookies array to follow symbols sorting 2022-06-16 19:42:21 -07:00
bpf_trace.h
error_report-traces.c tracing: add error_report_end trace point 2021-02-26 09:41:02 -08:00
fgraph.c arm64 fixes for 5.19-rc1: 2022-06-03 14:05:34 -07:00
fprobe.c fprobe: Resolve symbols with ftrace_lookup_symbols 2022-05-10 14:42:06 -07:00
ftrace_internal.h
ftrace.c ftrace: Keep address offset in ftrace_lookup_symbols 2022-06-16 19:42:21 -07:00
Kconfig ftrace: Be more specific about arch impact when function tracer is enabled 2022-07-12 16:36:34 -04:00
kprobe_event_gen_test.c
Makefile tracing: Disable kcov on trace_preemptirq.c 2022-05-26 21:13:00 -04:00
pid_list.c tracing: Cleanup double word in comment 2022-04-26 17:58:50 -04:00
pid_list.h tracing: Create a sparse bitmask for pid filtering 2021-10-05 17:38:45 -04:00
power-traces.c
preemptirq_delay_test.c kernel: trace: preemptirq_delay_test: add cpu affinity 2021-02-02 17:02:07 -05:00
rethook.c rethook: Reject getting a rethook if RCU is not watching 2022-06-17 21:53:35 +02:00
ring_buffer_benchmark.c
ring_buffer.c ring-buffer: Have 32 bit time stamps use all 64 bits 2022-04-27 17:19:30 -04:00
rpm-traces.c
synth_event_gen_test.c tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
trace_benchmark.c
trace_benchmark.h
trace_boot.c tracing: Initialize integer variable to prevent garbage return value 2022-05-26 21:13:00 -04:00
trace_branch.c tracing: Merge irqflags + preempt counter. 2021-02-02 17:02:06 -05:00
trace_clock.c tracing: Do no increment trace_clock_global() by one 2021-06-18 09:10:00 -04:00
trace_dynevent.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_dynevent.h tracing: Add DYNAMIC flag for dynamic events 2021-08-18 18:10:32 -04:00
trace_entries.h trace: Add timerlat tracer 2021-06-25 19:57:24 -04:00
trace_eprobe.c tracing: Remove check of list iterator against head past the loop body 2022-04-27 17:19:31 -04:00
trace_event_perf.c tracing: Show size of requested perf buffer 2021-10-27 12:25:09 -04:00
trace_events_filter_test.h
trace_events_filter.c tracing: Fix comments of create_filter() 2022-05-26 21:13:01 -04:00
trace_events_hist.c tracing/histograms: Fix memory leak problem 2022-07-12 16:35:42 -04:00
trace_events_inject.c tracing: Support __rel_loc relative dynamic data location attribute 2021-12-06 15:37:21 -05:00
trace_events_synth.c tracing: Fix strncpy warning in trace_events_synth.c 2022-03-11 11:49:24 -05:00
trace_events_trigger.c tracing: Fix comments for event_trigger_separate_filter() 2022-05-26 22:03:52 -04:00
trace_events_user.c tracing: mark user_events as BROKEN 2022-04-02 10:32:14 -07:00
trace_events.c tracing updates for 5.19: 2022-05-29 10:31:36 -07:00
trace_export.c
trace_functions_graph.c tracing: in_irq() cleanup 2021-10-13 18:19:41 -04:00
trace_functions.c ftrace: disable preemption when recursion locked 2021-10-27 11:21:49 -04:00
trace_hwlat.c trace/hwlat: make use of the helper function kthread_run_on_cpu() 2022-01-15 16:30:24 +02:00
trace_irqsoff.c tracing: Merge irqflags + preempt counter. 2021-02-02 17:02:06 -05:00
trace_kdb.c kdb: Rename members of struct kdbtab_t 2021-07-27 17:05:06 +01:00
trace_kprobe_selftest.c
trace_kprobe_selftest.h
trace_kprobe.c tracing/kprobes: Check whether get_kretprobe() returns NULL in kretprobe_dispatcher() 2022-06-17 17:40:06 -04:00
trace_mmiotrace.c tracing: Remove definition of DEBUG in trace_mmiotrace.c 2021-02-02 17:02:07 -05:00
trace_nop.c
trace_osnoise.c tracing updates for 5.19: 2022-05-29 10:31:36 -07:00
trace_output.c tracing: Remove usage of list iterator after the loop body 2022-04-27 17:19:30 -04:00
trace_output.h
trace_preemptirq.c lockdep: Fix -Wunused-parameter for _THIS_IP_ 2022-04-05 10:24:34 +02:00
trace_printk.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_probe_tmpl.h tracing/probes: Have process_fetch_insn() take a void * instead of pt_regs 2021-08-19 09:09:03 -04:00
trace_probe.c eprobes: Remove redundant event type information 2022-02-25 12:07:01 -05:00
trace_probe.h eprobes: Remove redundant event type information 2022-02-25 12:07:01 -05:00
trace_recursion_record.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_sched_switch.c sched/tracing: Append prev_state to tp args instead 2022-05-12 00:37:11 +02:00
trace_sched_wakeup.c sched/tracing: Append prev_state to tp args instead 2022-05-12 00:37:11 +02:00
trace_selftest_dynamic.c
trace_selftest.c tracing: Reset the function filter after completing trampoline/graph selftest 2022-05-25 16:57:37 -04:00
trace_seq.c tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
trace_stack.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_stat.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_stat.h
trace_synth.h tracing: synth events: increase max fields count 2021-09-08 15:29:16 -04:00
trace_syscalls.c tracing: Make tp_printk work on syscall tracepoints 2022-04-26 17:58:52 -04:00
trace_uprobe.c tracing/uprobes: Remove unwanted initialization in __trace_uprobe_create() 2022-06-17 19:12:07 -04:00
trace.c tracing: Fix sleeping while atomic in kdb ftdump 2022-07-12 16:35:58 -04:00
trace.h tracing: Have existing event_command.parse() implementations use helpers 2022-04-26 17:58:50 -04:00
tracing_map.c tracing: Fix tracing_map_sort_entries() kernel-doc comment 2022-04-26 17:58:51 -04:00
tracing_map.h