From: Peter Zijlstra <peterz@infradead.org>
To: Jason Vas Dias <jason.vas.dias@gmail.com>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>, andi <andi@firstfloor.org>
Subject: Re: [PATCH v4.16-rc4 2/2] x86/vdso: on Intel, VDSO should handle CLOCK_MONOTONIC_RAW
Date: Wed, 14 Mar 2018 14:12:37 +0100 [thread overview]
Message-ID: <20180314131237.GL4064@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CALyZvKzbLi6K9DFwOXu7h--MdxWFv9A3==0xORuQ=KwtJx3ZrQ@mail.gmail.com>
On Wed, Mar 14, 2018 at 12:55:20PM +0000, Jason Vas Dias wrote:
> > While CPU_CLOCK is TSC based, there is no guarantee it has any
> > correlation to CLOCK_MONOTONIC_RAW (even if that is also TSC based).
> >
> > (although, I think I might have fixed that recently and it might just
> > work, but it's very much not guaranteed).
>
> Yes, I believe the CPU_CLOCK is effectively the converted TSC -
> it does appear to correlate well with the new CLOCK_MONOTONIC_RAW
> values from the patched VDSO.
It (now) runs at the same rate, but there is no guarantee for this, in
fact it didn't for a very long time.
Relying on this is broken.
next prev parent reply other threads:[~2018-03-14 13:12 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-12 7:01 [PATCH v4.16-rc4 2/2] x86/vdso: on Intel, VDSO should handle CLOCK_MONOTONIC_RAW Jason Vas Dias
2018-03-12 8:27 ` Peter Zijlstra
2018-03-13 23:45 ` Jason Vas Dias
2018-03-14 9:45 ` Peter Zijlstra
2018-03-14 12:55 ` Jason Vas Dias
2018-03-14 13:11 ` Peter Zijlstra
2018-03-14 13:12 ` Peter Zijlstra [this message]
2018-03-14 13:16 ` Peter Zijlstra
2018-03-14 13:29 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2018-03-12 9:14 Jason Vas Dias
2018-03-12 17:41 ` kbuild test robot
2018-03-12 5:44 Jason Vas Dias
2018-03-12 5:33 Jason Vas Dias
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