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Commit e82b8e4e authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Ingo Molnar
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x86: Add IRQ_TIME_ACCOUNTING 



This patch adds IRQ_TIME_ACCOUNTING option on x86 and runtime enables it
when TSC is enabled.

This change just enables fine grained irq time accounting, isn't used yet.
Following patches use it for different purposes.

Signed-off-by: default avatarVenkatesh Pallipadi <venki@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1286237003-12406-6-git-send-email-venki@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b52bfee4

Documentation/kernel-parameters.txt

+4 −0
Original line number Diff line number Diff line
@@ -2435,6 +2435,10 @@ and is between 256 and 4096 characters. It is defined in the file 
			disables clocksource verification at runtime.

			Used to enable high-resolution timer mode on older

			hardware, and in virtualized environment.

			[x86] noirqtime: Do not use TSC to do irq accounting.

			Used to run time disable IRQ_TIME_ACCOUNTING on any

			platforms where RDTSC is slow and this accounting

			can add overhead.



	turbografx.map[2|3]=	[HW,JOY]

			TurboGraFX parallel port interface

arch/x86/Kconfig

+11 −0
Original line number Diff line number Diff line
@@ -795,6 +795,17 @@ 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

arch/x86/kernel/tsc.c

+8 −0
Original line number Diff line number Diff line
@@ -104,10 +104,14 @@ 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))

		no_sched_irq_time = 1;

	return 1;

}
@@ -801,6 +805,7 @@ void mark_tsc_unstable(char *reason) 
	if (!tsc_unstable) {

		tsc_unstable = 1;

		sched_clock_stable = 0;

		disable_sched_clock_irqtime();

		printk(KERN_INFO "Marking TSC unstable due to %s\n", reason);

		/* Change only the rating, when not registered */

		if (clocksource_tsc.mult)
@@ -987,6 +992,9 @@ void __init tsc_init(void) 
	/* now allow native_sched_clock() to use rdtsc */

	tsc_disabled = 0;



	if (!no_sched_irq_time)

		enable_sched_clock_irqtime();



	lpj = ((u64)tsc_khz * 1000);

	do_div(lpj, HZ);

	lpj_fine = lpj;