From: Thomas Gleixner <tglx@linutronix.de>
To: Pasha Tatashin <pasha.tatashin@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com,
hpa@zytor.com
Subject: Re: [v1 0/9] Early boot time stamps for x86
Date: Thu, 23 Mar 2017 11:56:17 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1703231146060.3982@nanos> (raw)
In-Reply-To: <a3f027ee-c193-2e1f-4f4c-da6cffb80d05@oracle.com>
On Wed, 22 Mar 2017, Pasha Tatashin wrote:
> Yes, I am certain it is 0 or near 0 on reset on this machine. Because, I
Emphasis on "this machine'
It's not guaranteed especially not on reboot and not with creative BIOSes
fiddling with the TSC_ADJUST value.
- It CANNOT be used to measure BIOS boot time reliably
- If BIOS wreckaged TSC_ADJUST, then your whole time stamping goes out the
window once the kernel sanitized it.
See other mail.
Thanks,
tglx
next prev parent reply other threads:[~2017-03-23 10:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-22 20:24 Pavel Tatashin
2017-03-22 20:24 ` [v1 1/9] sched/clock: broken stable to unstable transfer Pavel Tatashin
2017-03-27 10:27 ` [tip:sched/urgent] sched/clock: Fix " tip-bot for Pavel Tatashin
2017-03-22 20:24 ` [v1 2/9] sched/clock: interface to allow timestamps early in boot Pavel Tatashin
2017-03-22 20:24 ` [v1 3/9] x86/cpu: determining x86 vendor early Pavel Tatashin
2017-03-22 20:24 ` [v1 4/9] x86/tsc: early MSR-based CPU/TSC frequency discovery Pavel Tatashin
2017-03-22 20:24 ` [v1 5/9] x86/tsc: disable early messages from quick_pit_calibrate Pavel Tatashin
2017-03-22 20:24 ` [v1 6/9] x86/tsc: use cpuid to determine TSC frequency Pavel Tatashin
2017-03-22 20:24 ` [v1 7/9] x86/tsc: use cpuid to determine CPU frequency Pavel Tatashin
2017-03-22 20:24 ` [v1 8/9] x86/tsc: tsc early Pavel Tatashin
2017-03-24 5:38 ` kbuild test robot
2017-03-22 20:24 ` [v1 9/9] x86/tsc: use " Pavel Tatashin
2017-03-22 20:27 ` [v1 0/9] Early boot time stamps for x86 Peter Zijlstra
2017-03-23 0:02 ` Pasha Tatashin
2017-03-22 20:28 ` Peter Zijlstra
2017-03-22 23:59 ` Pasha Tatashin
2017-03-23 10:56 ` Thomas Gleixner [this message]
2017-03-23 14:39 ` Pasha Tatashin
2017-03-23 18:40 ` Thomas Gleixner
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