Messages in this thread Patch in this message | | | From | Joel Fernandes <> | Subject | [RFC v4 3/4] irqflags: Avoid unnecessary calls to trace_ if you can | Date | Mon, 16 Apr 2018 21:07:47 -0700 |
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With TRACE_IRQFLAGS, we call trace_ API too many times. We don't need to if local_irq_restore or local_irq_save didn't actually do anything.
This gives around a 4% improvement in performance when doing the following command: "time find / > /dev/null"
Also its best to avoid these calls where possible, since in this series, the RCU code in tracepoint.h seems to be call these quite a bit and I'd like to keep this overhead low.
Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zilstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Tom Zanussi <tom.zanussi@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Thomas Glexiner <tglx@linutronix.de> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Fenguang Wu <fengguang.wu@intel.com> Cc: Baohong Liu <baohong.liu@intel.com> Cc: Vedang Patel <vedang.patel@intel.com> Signed-off-by: Joel Fernandes <joelaf@google.com> --- include/linux/irqflags.h | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 9700f00bbc04..ea8df0ac57d3 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -104,19 +104,20 @@ do { \ #define local_irq_save(flags) \ do { \ raw_local_irq_save(flags); \ - trace_hardirqs_off(); \ + if (!raw_irqs_disabled_flags(flags)) \ + trace_hardirqs_off(); \ } while (0) -#define local_irq_restore(flags) \ - do { \ - if (raw_irqs_disabled_flags(flags)) { \ - raw_local_irq_restore(flags); \ - trace_hardirqs_off(); \ - } else { \ - trace_hardirqs_on(); \ - raw_local_irq_restore(flags); \ - } \ +#define local_irq_restore(flags) \ + do { \ + if (raw_irqs_disabled_flags(flags) && !irqs_disabled()) { \ + raw_local_irq_restore(flags); \ + trace_hardirqs_off(); \ + } else if (!raw_irqs_disabled_flags(flags) && irqs_disabled()) {\ + trace_hardirqs_on(); \ + raw_local_irq_restore(flags); \ + } \ } while (0) #define safe_halt() \ -- 2.17.0.484.g0c8726318c-goog
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