126 lines
5.4 KiB
Diff
126 lines
5.4 KiB
Diff
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Date: Wed, 22 Jan 2014 22:08:14 +0100
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From: Peter Zijlstra <peterz@infradead.org>
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To: Markus Trippelsdorf <markus@trippelsdorf.de>
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Cc: Sasha Levin <sasha.levin@oracle.com>,
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Arjan van de Ven <arjan@linux.intel.com>, lenb@kernel.org,
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rjw@rjwysocki.net, Eliezer Tamir <eliezer.tamir@linux.intel.com>,
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rui.zhang@intel.com, jacob.jun.pan@linux.intel.com,
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linux-kernel@vger.kernel.org, dyoung@redhat.com
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Subject: Re: [PATCH 13/15] sched: Use a static_key for sched_clock_stable
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Sender: linux-kernel-owner@vger.kernel.org
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X-Mailing-List: linux-kernel@vger.kernel.org
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>
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> I think its the right region to look through. My current suspect is the
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> linear continuity fit with the initial 'random' multiplier.
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>
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> That initial 'random' multiplier can get us quite high, and we'll fit
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> the function to match that but continue at a sane rate.
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>
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> I'll try and prod a little more later this evening as time permits.
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Does this cure things?
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---
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arch/x86/kernel/tsc.c | 11 +++++++----
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1 file changed, 7 insertions(+), 4 deletions(-)
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diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
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index a3acbac2ee72..bb04148c5fe0 100644
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--- a/arch/x86/kernel/tsc.c
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+++ b/arch/x86/kernel/tsc.c
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@@ -237,7 +237,7 @@ static inline unsigned long long cycles_2_ns(unsigned long long cyc)
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/* XXX surely we already have this someplace in the kernel?! */
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#define DIV_ROUND(n, d) (((n) + ((d) / 2)) / (d))
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-static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
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+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu, bool origin)
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{
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unsigned long long tsc_now, ns_now;
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struct cyc2ns_data *data;
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@@ -252,7 +252,10 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
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data = cyc2ns_write_begin(cpu);
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rdtscll(tsc_now);
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- ns_now = cycles_2_ns(tsc_now);
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+ if (origin)
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+ ns_now = 0;
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+ else
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+ ns_now = cycles_2_ns(tsc_now);
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/*
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* Compute a new multiplier as per the above comment and ensure our
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@@ -926,7 +929,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
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mark_tsc_unstable("cpufreq changes");
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}
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- set_cyc2ns_scale(tsc_khz, freq->cpu);
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+ set_cyc2ns_scale(tsc_khz, freq->cpu, false);
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return 0;
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}
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@@ -1199,7 +1202,7 @@ void __init tsc_init(void)
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*/
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for_each_possible_cpu(cpu) {
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cyc2ns_init(cpu);
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- set_cyc2ns_scale(cpu_khz, cpu);
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+ set_cyc2ns_scale(cpu_khz, cpu, true);
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}
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if (tsc_disabled > 0)
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--
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