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Message-ID: <20110106101555.GA22750@elte.hu>
Date: Thu, 6 Jan 2011 11:15:55 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] x86/tsc changes for v2.6.38
Linus,
Please pull the latest x86-tsc-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git x86-tsc-for-linus
Thanks,
Ingo
------------------>
John Stultz (2):
x86: Make tsc=reliable override boot time stability checks
x86: Improve TSC calibration using a delayed workqueue
Thomas Gleixner (1):
x86: Check tsc available/disabled in the delayed init function
Documentation/kernel-parameters.txt | 9 ++--
arch/x86/kernel/tsc.c | 96 +++++++++++++++++++++++++++++++++--
2 files changed, 96 insertions(+), 9 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 92e83e5..c7c8eca 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2467,12 +2467,13 @@ and is between 256 and 4096 characters. It is defined in the file
to facilitate early boot debugging.
See also Documentation/trace/events.txt
- tsc= Disable clocksource-must-verify flag for TSC.
+ tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
- disables clocksource verification at runtime.
- Used to enable high-resolution timer mode on older
- hardware, and in virtualized environment.
+ disables clocksource verification at runtime, as well
+ as the stability checks done at bootup. 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
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 0c40d8b..356a0d4 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -872,6 +872,9 @@ __cpuinit int unsynchronized_tsc(void)
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
return 0;
+
+ if (tsc_clocksource_reliable)
+ return 0;
/*
* Intel systems are normally all synchronized.
* Exceptions must mark TSC as unstable:
@@ -879,14 +882,92 @@ __cpuinit int unsynchronized_tsc(void)
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
/* assume multi socket systems are not synchronized: */
if (num_possible_cpus() > 1)
- tsc_unstable = 1;
+ return 1;
}
- return tsc_unstable;
+ return 0;
+}
+
+
+static void tsc_refine_calibration_work(struct work_struct *work);
+static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
+/**
+ * tsc_refine_calibration_work - Further refine tsc freq calibration
+ * @work - ignored.
+ *
+ * This functions uses delayed work over a period of a
+ * second to further refine the TSC freq value. Since this is
+ * timer based, instead of loop based, we don't block the boot
+ * process while this longer calibration is done.
+ *
+ * If there are any calibration anomolies (too many SMIs, etc),
+ * or the refined calibration is off by 1% of the fast early
+ * calibration, we throw out the new calibration and use the
+ * early calibration.
+ */
+static void tsc_refine_calibration_work(struct work_struct *work)
+{
+ static u64 tsc_start = -1, ref_start;
+ static int hpet;
+ u64 tsc_stop, ref_stop, delta;
+ unsigned long freq;
+
+ /* Don't bother refining TSC on unstable systems */
+ if (check_tsc_unstable())
+ goto out;
+
+ /*
+ * Since the work is started early in boot, we may be
+ * delayed the first time we expire. So set the workqueue
+ * again once we know timers are working.
+ */
+ if (tsc_start == -1) {
+ /*
+ * Only set hpet once, to avoid mixing hardware
+ * if the hpet becomes enabled later.
+ */
+ hpet = is_hpet_enabled();
+ schedule_delayed_work(&tsc_irqwork, HZ);
+ tsc_start = tsc_read_refs(&ref_start, hpet);
+ return;
+ }
+
+ tsc_stop = tsc_read_refs(&ref_stop, hpet);
+
+ /* hpet or pmtimer available ? */
+ if (!hpet && !ref_start && !ref_stop)
+ goto out;
+
+ /* Check, whether the sampling was disturbed by an SMI */
+ if (tsc_start == ULLONG_MAX || tsc_stop == ULLONG_MAX)
+ goto out;
+
+ delta = tsc_stop - tsc_start;
+ delta *= 1000000LL;
+ if (hpet)
+ freq = calc_hpet_ref(delta, ref_start, ref_stop);
+ else
+ freq = calc_pmtimer_ref(delta, ref_start, ref_stop);
+
+ /* Make sure we're within 1% */
+ if (abs(tsc_khz - freq) > tsc_khz/100)
+ goto out;
+
+ tsc_khz = freq;
+ printk(KERN_INFO "Refined TSC clocksource calibration: "
+ "%lu.%03lu MHz.\n", (unsigned long)tsc_khz / 1000,
+ (unsigned long)tsc_khz % 1000);
+
+out:
+ clocksource_register_khz(&clocksource_tsc, tsc_khz);
}
-static void __init init_tsc_clocksource(void)
+
+static int __init init_tsc_clocksource(void)
{
+ if (!cpu_has_tsc || tsc_disabled > 0)
+ return 0;
+
if (tsc_clocksource_reliable)
clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
/* lower the rating if we already know its unstable: */
@@ -894,8 +975,14 @@ static void __init init_tsc_clocksource(void)
clocksource_tsc.rating = 0;
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
}
- clocksource_register_khz(&clocksource_tsc, tsc_khz);
+ schedule_delayed_work(&tsc_irqwork, 0);
+ return 0;
}
+/*
+ * We use device_initcall here, to ensure we run after the hpet
+ * is fully initialized, which may occur at fs_initcall time.
+ */
+device_initcall(init_tsc_clocksource);
void __init tsc_init(void)
{
@@ -949,6 +1036,5 @@ void __init tsc_init(void)
mark_tsc_unstable("TSCs unsynchronized");
check_system_tsc_reliable();
- init_tsc_clocksource();
}
--
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