linux-kernel - Re: [PATCH] scheduler: fix x86 regression in native_sched

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Message-ID: <20071207085121.GA12625@elte.hu>
Date:	Fri, 7 Dec 2007 09:51:21 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Guillaume Chazarain <guichaz@...oo.fr>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Stefano Brivio <stefano.brivio@...imi.it>,
	Robert Love <rml@...h9.net>, linux-kernel@...r.kernel.org,
	Dave Jones <davej@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Michael Buesch <mb@...sch.de>,
	"Andrew Morton"@pimp.vs19.net
Subject: Re: [PATCH] scheduler: fix x86 regression in native_sched_clock


* Guillaume Chazarain <guichaz@...oo.fr> wrote:

> > Something like http://lkml.org/lkml/2007/3/16/291 that would need 
> > some refresh?
> 
> And here is a refreshed one just for testing with 2.6-git. The 64 bit 
> part is a shamelessly untested copy/paste as I cannot test it.

yeah, we can do something like this in 2.6.25 - this will improve the 
quality of sched_clock(). The other patch i sent should solve the 
problem for 2.6.24 - printk should not be using raw sched_clock() calls. 
(as the name says it's for the scheduler's internal use.) I've also 
queued up the patch below - it removes the now unnecessary printk clock 
code.

	Ingo

--------------------->
Subject: sched: remove printk_clock()
From: Ingo Molnar <mingo@...e.hu>

printk_clock() is obsolete - it has been replaced with cpu_clock().

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/arm/kernel/time.c  |   11 -----------
 arch/ia64/kernel/time.c |   27 ---------------------------
 kernel/printk.c         |    5 -----
 3 files changed, 43 deletions(-)

Index: linux/arch/arm/kernel/time.c
===================================================================
--- linux.orig/arch/arm/kernel/time.c
+++ linux/arch/arm/kernel/time.c
@@ -79,17 +79,6 @@ static unsigned long dummy_gettimeoffset
 }
 #endif
 
-/*
- * An implementation of printk_clock() independent from
- * sched_clock().  This avoids non-bootable kernels when
- * printk_clock is enabled.
- */
-unsigned long long printk_clock(void)
-{
-	return (unsigned long long)(jiffies - INITIAL_JIFFIES) *
-			(1000000000 / HZ);
-}
-
 static unsigned long next_rtc_update;
 
 /*
Index: linux/arch/ia64/kernel/time.c
===================================================================
--- linux.orig/arch/ia64/kernel/time.c
+++ linux/arch/ia64/kernel/time.c
@@ -344,33 +344,6 @@ udelay (unsigned long usecs)
 }
 EXPORT_SYMBOL(udelay);
 
-static unsigned long long ia64_itc_printk_clock(void)
-{
-	if (ia64_get_kr(IA64_KR_PER_CPU_DATA))
-		return sched_clock();
-	return 0;
-}
-
-static unsigned long long ia64_default_printk_clock(void)
-{
-	return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES) *
-		(1000000000/HZ);
-}
-
-unsigned long long (*ia64_printk_clock)(void) = &ia64_default_printk_clock;
-
-unsigned long long printk_clock(void)
-{
-	return ia64_printk_clock();
-}
-
-void __init
-ia64_setup_printk_clock(void)
-{
-	if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT))
-		ia64_printk_clock = ia64_itc_printk_clock;
-}
-
 /* IA64 doesn't cache the timezone */
 void update_vsyscall_tz(void)
 {
Index: linux/kernel/printk.c
===================================================================
--- linux.orig/kernel/printk.c
+++ linux/kernel/printk.c
@@ -573,11 +573,6 @@ static int __init printk_time_setup(char
 
 __setup("time", printk_time_setup);
 
-__attribute__((weak)) unsigned long long printk_clock(void)
-{
-	return sched_clock();
-}
-
 /* Check if we have any console registered that can be called early in boot. */
 static int have_callable_console(void)
 {
--
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