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Message-ID: <CABeCy1YsLKc14uLGzxRC95Q7v-r2Qkx6Ohzcf4rYUVv4sYfrYg@mail.gmail.com>
Date: Wed, 8 Feb 2012 14:50:34 -0800
From: Venki Pallipadi <venki@...gle.com>
To: Dmitry Antipov <dmitry.antipov@...aro.org>
Cc: Russell King <linux@....linux.org.uk>,
Rusty Russell <rusty@...tcorp.com.au>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
linaro-dev@...ts.linaro.org, patches@...aro.org
Subject: Re: [PATCH] sched: generalize CONFIG_IRQ_TIME_ACCOUNTING for X86 and ARM
On Wed, Feb 8, 2012 at 8:08 AM, Dmitry Antipov
<dmitry.antipov@...aro.org> wrote:
> Generalize CONFIG_IRQ_TIME_ACCOUNTING between X86 and
> ARM, move "noirqtime=" option to common debugging code.
> For a bit of backward compatibility, X86-specific option
> "tsc=noirqtime" is preserved, but issues a warning.
>
> Suggested-by: Russell King <rmk+kernel@....linux.org.uk>
> Suggested-by: Venki Pallipadi <venki@...gle.com>
> Signed-off-by: Dmitry Antipov <dmitry.antipov@...aro.org>
> ---
> arch/arm/kernel/sched_clock.c | 3 +++
> arch/x86/Kconfig | 11 -----------
> arch/x86/kernel/tsc.c | 7 ++++---
> include/linux/sched.h | 2 ++
> lib/Kconfig.debug | 12 ++++++++++++
> lib/Makefile | 2 ++
> lib/irqtime.c | 12 ++++++++++++
> 7 files changed, 35 insertions(+), 14 deletions(-)
> create mode 100644 lib/irqtime.c
>
> diff --git a/arch/arm/kernel/sched_clock.c b/arch/arm/kernel/sched_clock.c
> index 5416c7c..961bd2d 100644
> --- a/arch/arm/kernel/sched_clock.c
> +++ b/arch/arm/kernel/sched_clock.c
> @@ -144,6 +144,9 @@ void __init setup_sched_clock(u32 (*read)(void), int bits, unsigned long rate)
> */
> cd.epoch_ns = 0;
>
> + if (!no_sched_irq_time)
> + enable_sched_clock_irqtime();
> +
> pr_debug("Registered %pF as sched_clock source\n", read);
> }
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 5bed94e..4759676 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -805,17 +805,6 @@ config SCHED_MC
> making when dealing with multi-core CPU chips at a cost of slightly
> increased overhead in some places. If unsure say N here.
>
> -config IRQ_TIME_ACCOUNTING
> - bool "Fine granularity task level IRQ time accounting"
> - default n
> - ---help---
> - Select this option to enable fine granularity task irq time
> - accounting. This is done by reading a timestamp on each
> - transitions between softirq and hardirq state, so there can be a
> - small performance impact.
> -
> - If in doubt, say N here.
> -
> source "kernel/Kconfig.preempt"
>
> config X86_UP_APIC
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index a62c201..70510a3 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -103,14 +103,15 @@ int __init notsc_setup(char *str)
>
> __setup("notsc", notsc_setup);
>
> -static int no_sched_irq_time;
> -
> static int __init tsc_setup(char *str)
> {
> if (!strcmp(str, "reliable"))
> tsc_clocksource_reliable = 1;
> - if (!strncmp(str, "noirqtime", 9))
> + if (!strncmp(str, "noirqtime", 9)) {
> + printk(KERN_WARNING "tsc: tsc=noirqtime is "
> + "obsolete, use noirqtime instead\n");
> no_sched_irq_time = 1;
> + }
> return 1;
> }
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 7d379a6..b3575b5 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1966,9 +1966,11 @@ extern void sched_clock_idle_wakeup_event(u64 delta_ns);
> * The reason for this explicit opt-in is not to have perf penalty with
> * slow sched_clocks.
> */
> +extern int no_sched_irq_time;
> extern void enable_sched_clock_irqtime(void);
> extern void disable_sched_clock_irqtime(void);
> #else
> +#define no_sched_irq_time 1
> static inline void enable_sched_clock_irqtime(void) {}
> static inline void disable_sched_clock_irqtime(void) {}
> #endif
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 8745ac7..236e814 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -299,6 +299,18 @@ config SCHEDSTATS
> application, you can say N to avoid the very slight overhead
> this adds.
>
> +config IRQ_TIME_ACCOUNTING
> + bool "Fine granularity task level IRQ time accounting"
> + depends on X86 || ARM
> + default n
> + ---help---
> + Select this option to enable fine granularity task irq time
> + accounting. This is done by reading a timestamp on each
> + transitions between softirq and hardirq state, so there can be a
> + small performance impact.
> +
> + If in doubt, say N here.
> +
> config TIMER_STATS
> bool "Collect kernel timers statistics"
> depends on DEBUG_KERNEL && PROC_FS
> diff --git a/lib/Makefile b/lib/Makefile
> index 18515f0..44d67d4 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -49,6 +49,8 @@ obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
> obj-$(CONFIG_DEBUG_LIST) += list_debug.o
> obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
>
> +obj-$(CONFIG_IRQ_TIME_ACCOUNTING) += irqtime.o
> +
> ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
> lib-y += dec_and_lock.o
> endif
> diff --git a/lib/irqtime.c b/lib/irqtime.c
> new file mode 100644
> index 0000000..10d440d
> --- /dev/null
> +++ b/lib/irqtime.c
> @@ -0,0 +1,12 @@
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +
> +int no_sched_irq_time;
> +
> +static int __init irqtime_setup(char *str)
> +{
> + no_sched_irq_time = 1;
> + return 1;
> +}
> +
> +__setup("noirqtime", irqtime_setup);
> --
One more nit-pick. We need corresponding change in
Documentation/kernel-parameters.txt to deprecate tsc=irqtime and add
this new param.
> 1.7.7.6
>
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