117 lines
5.2 KiB
Diff
117 lines
5.2 KiB
Diff
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Delivered-To: jwboyer@gmail.com
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id 0B4E580383F6; Thu, 23 Jan 2014 10:48:04 +0100 (CET)
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Date: Thu, 23 Jan 2014 10:48:04 +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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Mike Galbraith <bitbucket@online.de>,
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Andy Lutomirski <luto@amacapital.net>,
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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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Message-ID: <20140123094804.GP30183@twins.programming.kicks-ass.net>
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References: <20140122123022.GN31570@twins.programming.kicks-ass.net>
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<20140122131456.GA389@x4>
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<52DFD50E.800@oracle.com>
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<20140122183538.GA389@x4>
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<20140122184253.GN30183@twins.programming.kicks-ass.net>
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<20140122190905.GA391@x4>
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<20140122191254.GA390@x4>
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<20140122201605.GU11314@laptop.programming.kicks-ass.net>
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<20140122210814.GC9481@laptop.programming.kicks-ass.net>
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<20140122211740.GA391@x4>
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Sender: linux-kernel-owner@vger.kernel.org
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On Wed, Jan 22, 2014 at 10:17:40PM +0100, Markus Trippelsdorf wrote:
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> Yes. Thanks Peter.
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>
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Ah much simpler patch that should have the same effect:
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---
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Subject: sched/x86/tsc: Initialize multiplier to 0
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From: Peter Zijlstra <peterz@infradead.org>
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Date: Wed, 22 Jan 2014 22:08:14 +0100
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Since we keep the clock value linearly continuous on frequency change,
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make sure the initial multiplier is 0, such that out initial value is
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0. Without this we compute the initial value at whatever the TSC has
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managed to reach since power-on.
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Fixes: 20d1c86a57762 ("sched/clock, x86: Rewrite cyc2ns() to avoid the need to disable IRQs")
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Cc: lenb@kernel.org
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Cc: rjw@rjwysocki.net
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Cc: Eliezer Tamir <eliezer.tamir@linux.intel.com>
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Cc: rui.zhang@intel.com
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Cc: jacob.jun.pan@linux.intel.com
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Cc: Mike Galbraith <bitbucket@online.de>
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Cc: Ingo Molnar <mingo@kernel.org>
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Cc: hpa@zytor.com
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Cc: paulmck@linux.vnet.ibm.com
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: John Stultz <john.stultz@linaro.org>
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Cc: Andy Lutomirski <luto@amacapital.net>
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Cc: Arjan van de Ven <arjan@linux.intel.com>
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Cc: Sasha Levin <sasha.levin@oracle.com>
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Cc: dyoung@redhat.com
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Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
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Signed-off-by: Peter Zijlstra <peterz@infradead.org>
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---
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arch/x86/kernel/tsc.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/arch/x86/kernel/tsc.c
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+++ b/arch/x86/kernel/tsc.c
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@@ -180,7 +180,7 @@ static void cyc2ns_write_end(int cpu, st
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static void cyc2ns_data_init(struct cyc2ns_data *data)
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{
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- data->cyc2ns_mul = 1U << CYC2NS_SCALE_FACTOR;
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+ data->cyc2ns_mul = 0;
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data->cyc2ns_shift = CYC2NS_SCALE_FACTOR;
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data->cyc2ns_offset = 0;
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data->__count = 0;
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--
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