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-rw-r--r--peterz-printk-timestamp-fix.patch131
1 files changed, 61 insertions, 70 deletions
diff --git a/peterz-printk-timestamp-fix.patch b/peterz-printk-timestamp-fix.patch
index d942b2de0..825f4f749 100644
--- a/peterz-printk-timestamp-fix.patch
+++ b/peterz-printk-timestamp-fix.patch
@@ -1,31 +1,31 @@
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+Date: Thu, 23 Jan 2014 10:48:04 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Sasha Levin <sasha.levin@oracle.com>,
@@ -39,10 +39,8 @@ Cc: Sasha Levin <sasha.levin@oracle.com>,
Andy Lutomirski <luto@amacapital.net>,
linux-kernel@vger.kernel.org, dyoung@redhat.com
Subject: Re: [PATCH 13/15] sched: Use a static_key for sched_clock_stable
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+References: <20140122123022.GN31570@twins.programming.kicks-ass.net>
<20140122131456.GA389@x4>
<52DFD50E.800@oracle.com>
<20140122183538.GA389@x4>
@@ -50,74 +48,67 @@ References: <20140122120757.GL31570@twins.programming.kicks-ass.net>
<20140122190905.GA391@x4>
<20140122191254.GA390@x4>
<20140122201605.GU11314@laptop.programming.kicks-ass.net>
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+On Wed, Jan 22, 2014 at 10:17:40PM +0100, Markus Trippelsdorf wrote:
+> Yes. Thanks Peter.
>
-> I think its the right region to look through. My current suspect is the
-> linear continuity fit with the initial 'random' multiplier.
->
-> That initial 'random' multiplier can get us quite high, and we'll fit
-> the function to match that but continue at a sane rate.
->
-> I'll try and prod a little more later this evening as time permits.
-Does this cure things?
+Ah much simpler patch that should have the same effect:
+
+---
+Subject: sched/x86/tsc: Initialize multiplier to 0
+From: Peter Zijlstra <peterz@infradead.org>
+Date: Wed, 22 Jan 2014 22:08:14 +0100
+
+Since we keep the clock value linearly continuous on frequency change,
+make sure the initial multiplier is 0, such that out initial value is
+0. Without this we compute the initial value at whatever the TSC has
+managed to reach since power-on.
+Fixes: 20d1c86a57762 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs")
+Cc: lenb@kernel.org
+Cc: rjw@rjwysocki.net
+Cc: Eliezer Tamir <eliezer.tamir@linux.intel.com>
+Cc: rui.zhang@intel.com
+Cc: jacob.jun.pan@linux.intel.com
+Cc: Mike Galbraith <bitbucket@online.de>
+Cc: Ingo Molnar <mingo@kernel.org>
+Cc: hpa@zytor.com
+Cc: paulmck@linux.vnet.ibm.com
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: John Stultz <john.stultz@linaro.org>
+Cc: Andy Lutomirski <luto@amacapital.net>
+Cc: Arjan van de Ven <arjan@linux.intel.com>
+Cc: Sasha Levin <sasha.levin@oracle.com>
+Cc: dyoung@redhat.com
+Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
+Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
- arch/x86/kernel/tsc.c | 11 +++++++----
- 1 file changed, 7 insertions(+), 4 deletions(-)
+ arch/x86/kernel/tsc.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
-diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
-index a3acbac2ee72..bb04148c5fe0 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
-@@ -237,7 +237,7 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
- /* XXX surely we already have this someplace in the kernel?! */
- #define DIV_ROUND(n, d) (((n) + ((d) / 2)) / (d))
+@@ -180,7 +180,7 @@ static void cyc2ns_write_end(int cpu, st
--static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
-+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu, bool origin)
+ static void cyc2ns_data_init(struct cyc2ns_data *data)
{
- unsigned long long tsc_now, ns_now;
- struct cyc2ns_data *data;
-@@ -252,7 +252,10 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
- data = cyc2ns_write_begin(cpu);
-
- rdtscll(tsc_now);
-- ns_now = cycles_2_ns(tsc_now);
-+ if (origin)
-+ ns_now = 0;
-+ else
-+ ns_now = cycles_2_ns(tsc_now);
-
- /*
- * Compute a new multiplier as per the above comment and ensure our
-@@ -926,7 +929,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
- mark_tsc_unstable("cpufreq changes");
- }
-
-- set_cyc2ns_scale(tsc_khz, freq->cpu);
-+ set_cyc2ns_scale(tsc_khz, freq->cpu, false);
-
- return 0;
- }
-@@ -1199,7 +1202,7 @@ void __init tsc_init(void)
- */
- for_each_possible_cpu(cpu) {
- cyc2ns_init(cpu);
-- set_cyc2ns_scale(cpu_khz, cpu);
-+ set_cyc2ns_scale(cpu_khz, cpu, true);
- }
-
- if (tsc_disabled > 0)
+- data->cyc2ns_mul = 1U << CYC2NS_SCALE_FACTOR;
++ data->cyc2ns_mul = 0;
+ data->cyc2ns_shift = CYC2NS_SCALE_FACTOR;
+ data->cyc2ns_offset = 0;
+ data->__count = 0;
--
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