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tracing: Remove obsolete PREEMPTIRQ_EVENTS kconfig option 

The PREEMPTIRQ_EVENTS option is unused after commit c3bc8fd637 ("tracing:
Centralize preemptirq tracepoints and unify their usage"). Remove it.

Note that this option is hazardous as it stands. It enables TRACE_IRQFLAGS
event on non-preempt configurations without the irqsoff tracer enabled.
TRACE_IRQFLAGS as it stands incurs significant overhead on each IRQ
entry/exit. This is because trace_hardirqs_[on|off] does all the per-cpu
manipulations and NMI checks even if tracing is completely disabled for
some insane reason.  For example, netperf running UDP_STREAM on localhost
incurs a 4-6% performance penalty without any tracing if IRQFLAGS is
set. It can be put behind a static brach but even the function entry/exit
costs a little bit.

Link: https://lkml.kernel.org/r/20200409104034.GJ3818@techsingularity.net

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Mel Gorman 2020-04-09 11:40:34 +01:00 committed by Steven Rostedt (VMware)
parent daceabf1b4
commit 388d8bdb87
1 changed files with 0 additions and 9 deletions
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9
kernel/trace/Kconfig
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@ -258,15 +258,6 @@ config TRACE_PREEMPT_TOGGLE
Enables hooks which will be called when preemption is first disabled, Enables hooks which will be called when preemption is first disabled,
and last enabled. and last enabled.
config PREEMPTIRQ_EVENTS
bool "Enable trace events for preempt and irq disable/enable"
select TRACE_IRQFLAGS
select TRACE_PREEMPT_TOGGLE if PREEMPTION
select GENERIC_TRACER
default n
help
Enable tracing of disable and enable events for preemption and irqs.
config IRQSOFF_TRACER config IRQSOFF_TRACER
bool "Interrupts-off Latency Tracer" bool "Interrupts-off Latency Tracer"
default n default n