Commit 388d8bdb authored by Mel Gorman's avatar Mel Gorman Committed by Steven Rostedt (VMware)
Browse files

tracing: Remove obsolete PREEMPTIRQ_EVENTS kconfig option 

The PREEMPTIRQ_EVENTS option is unused after commit c3bc8fd6 ("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: default avatarMel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent daceabf1

kernel/trace/Kconfig

+0 −9
Original line number Original line Diff line number Diff line
@@ -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