From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, haiyangz@microsoft.com, tglx@linutronix.de,
hpa@zytor.com, vkuznets@redhat.com, kys@microsoft.com,
torvalds@linux-foundation.org, linux-kernel@vger.kernel.org
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/platform] x86/hyperv: Mark the Hyper-V TSC as unstable
Date: Fri, 21 Aug 2015 16:34:15 +0200 [thread overview]
Message-ID: <20150821143415.GK3161@worktop.event.rightround.com> (raw)
In-Reply-To: <tip-88c9281a9fba67636ab26c1fd6afbc78a632374f@git.kernel.org>
On Fri, Aug 21, 2015 at 12:45:50AM -0700, tip-bot for Vitaly Kuznetsov wrote:
> Commit-ID: 88c9281a9fba67636ab26c1fd6afbc78a632374f
> Gitweb: http://git.kernel.org/tip/88c9281a9fba67636ab26c1fd6afbc78a632374f
> Author: Vitaly Kuznetsov <vkuznets@redhat.com>
> AuthorDate: Wed, 19 Aug 2015 09:54:24 -0700
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 21 Aug 2015 08:44:38 +0200
>
> x86/hyperv: Mark the Hyper-V TSC as unstable
>
> The Hyper-V top-level functional specification states, that
> "algorithms should be resilient to sudden jumps forward or
> backward in the TSC value", this means that we should consider
> TSC as unstable. In some cases tsc tests are able to detect the
> instability, it was detected in 543 out of 646 boots in my
> testing:
>
> Measured 6277 cycles TSC warp between CPUs, turning off TSC clock.
> tsc: Marking TSC unstable due to check_tsc_sync_source failed
>
> This is, however, just a heuristic. On Hyper-V platform there
> are two good clocksources: MSR-based hyperv_clocksource and
> recently introduced TSC page.
*groan*.. and where are the paravirt ops like pv_time_ops for hyperv to
fix up this mess?
next prev parent reply other threads:[~2015-08-21 14:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-19 16:54 [PATCH] hyper-v: mark " Vitaly Kuznetsov
2015-08-21 7:45 ` [tip:x86/platform] x86/hyperv: Mark the Hyper-V " tip-bot for Vitaly Kuznetsov
2015-08-21 14:34 ` Peter Zijlstra [this message]
2015-08-21 15:35 ` KY Srinivasan
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