From: Mel Gorman <mgorman@techsingularity.net>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Namhyung Kim <namhyung@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH] tracing: Remove obsolete PREEMPTIRQ_EVENTS kconfig option
Date: Thu, 9 Apr 2020 11:40:34 +0100 [thread overview]
Message-ID: <20200409104034.GJ3818@techsingularity.net> (raw)
The PREEMPTIRQ_EVENTS option is unused after commit c3bc8fd637a9 ("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.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
kernel/trace/Kconfig | 9 ---------
1 file changed, 9 deletions(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 402eef84c859..568ad371e19c 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -258,15 +258,6 @@ config TRACE_PREEMPT_TOGGLE
Enables hooks which will be called when preemption is first disabled,
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
bool "Interrupts-off Latency Tracer"
default n
reply other threads:[~2020-04-09 10:40 UTC|newest]
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