linux-kernel - Re: [PATCH 6/6] cputime: Make finegrained irqtime accounting generally available

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Date:	Mon, 10 Sep 2012 21:53:38 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH 6/6] cputime: Make finegrained irqtime accounting
 generally available

On Mon, Sep 10, 2012 at 09:43:13PM +0200, Frederic Weisbecker wrote:
> There is no known reason for this option to be unavailable on other
> archs than x86. They just need to call enable_sched_clock_irqtime()
> if they have a sufficiently finegrained clock to make it working.
> 
> Move it to the general option and let the user choose between
> it and pure tick based or virtual cputime accounting.
> 
> Note that virtual cputime accounting already performs a finegrained
> irqtime accounting. CONFIG_IRQ_TIME_ACCOUNTING is a kind of middle ground
> between tick and virtual based accounting. So CONFIG_IRQ_TIME_ACCOUNTING
> and CONFIG_VIRT_CPU_ACCOUNTING are mutually exclusive choices.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Russell King <linux@....linux.org.uk>
> ---
>  arch/Kconfig     |    6 ++++++
>  arch/x86/Kconfig |   12 +-----------
>  init/Kconfig     |   30 +++++++++++++++++++++++++++++-
>  3 files changed, 36 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index f78de57..101c31a 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -284,4 +284,10 @@ config SECCOMP_FILTER
>  config HAVE_VIRT_CPU_ACCOUNTING
>  	bool
>  
> +config HAVE_IRQ_TIME_ACCOUNTING
> +	bool
> +	help
> +	  Archs need to ensure they use a high enough resolution clock to
> +	  support irq time accounting and then call enable_sched_clock_irqtime().
> +
>  source "kernel/gcov/Kconfig"
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 8ec3a1a..b86833a 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -97,6 +97,7 @@ config X86
>  	select KTIME_SCALAR if X86_32
>  	select GENERIC_STRNCPY_FROM_USER
>  	select GENERIC_STRNLEN_USER
> +	select HAVE_IRQ_TIME_ACCOUNTING
>  
>  config INSTRUCTION_DECODER
>  	def_bool (KPROBES || PERF_EVENTS || UPROBES)
> @@ -796,17 +797,6 @@ 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/init/Kconfig b/init/Kconfig
> index 2c5aa34..054114e 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -326,10 +326,25 @@ source "kernel/time/Kconfig"
>  
>  menu "CPU/Task time and stats accounting"
>  
> +choice
> +	prompt "Cputime accounting"
> +	default TICK_CPU_ACCOUNTING if !PPC64
> +	default VIRT_CPU_ACCOUNTING if PPC64
> +
> +# Kind of a stub config for the pure tick based cputime accounting
> +config TICK_CPU_ACCOUNTING
> +	bool "Simple tick based cputime accounting"
> +	depends on !S390
> +	help
> +	  This is the basic tick based cputime accounting that maintains
> +	  statistics about user, system and idle time spent on per jiffies
> +	  granularity.
> +
> +	  If unsure, say Y.
> +
>  config VIRT_CPU_ACCOUNTING
>  	bool "Deterministic task and CPU time accounting"
>  	depends on HAVE_VIRT_CPU_ACCOUNTING
> -	default y if PPC64
>  	help
>  	  Select this option to enable more accurate task and CPU time
>  	  accounting.  This is done by reading a CPU counter on each
> @@ -339,6 +354,19 @@ config VIRT_CPU_ACCOUNTING
>  	  this also enables accounting of stolen time on logically-partitioned
>  	  systems.
>  
> +config IRQ_TIME_ACCOUNTING
> +	bool "Fine granularity task level IRQ time accounting"
> +	depends on !S390 && HAVE_IRQ_TIME_ACCOUNTING

As Russell King pointed me, I don't need the !S390 here because it doesn't
select HAVE_IRQ_TIME_ACCOUNT anyway. I'll fix this. Just waiting for more
reviews before sending a v2.

Thanks.


> +	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.
> +
> +endchoice
> +
>  config BSD_PROCESS_ACCT
>  	bool "BSD Process Accounting"
>  	help
> -- 
> 1.7.5.4
> 
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