Messages in this thread | | | Date | Mon, 19 Jun 2023 18:58:24 +0200 | Subject | Re: [PATCH 1/1] clocksource: hyper-v: Rework clocksource and sched clock setup | From | Daniel Lezcano <> |
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On 19/06/2023 18:44, Michael Kelley (LINUX) wrote: > From: Daniel Lezcano <daniel.lezcano@linaro.org> Sent: Monday, June 19, 2023 9:16 AM >> >> On 09/06/2023 17:47, Michael Kelley wrote: >>> Current code assigns either the Hyper-V TSC page or MSR-based ref counter >>> as the sched clock. This may be sub-optimal in two cases. First, if there >>> is hardware support to ensure consistent TSC frequency across live >>> migrations and Hyper-V is using that support, the raw TSC is a faster >>> source of time than the Hyper-V TSC page. Second, the MSR-based ref >>> counter is relatively slow because reads require a trap to the hypervisor. >>> As such, it should never be used as the sched clock. The native sched >>> clock based on the raw TSC or jiffies is much better. >>> >>> Rework the sched clock setup so it is set to the TSC page only if >>> Hyper-V indicates that the TSC may have inconsistent frequency across >>> live migrations. Also, remove the code that sets the sched clock to >>> the MSR-based ref counter. In the cases where it is not set, the sched >>> clock will then be the native sched clock. >>> >>> As part of the rework, always enable both the TSC page clocksource and >>> the MSR-based ref counter clocksource. Set the ratings so the TSC page >>> clocksource is preferred. While the MSR-based ref counter clocksource >>> is unlikely to ever be the default, having it available for manual >>> selection is convenient for development purposes. >>> >>> Signed-off-by: Michael Kelley <mikelley@microsoft.com> >> >> The patch does not apply, does it depend on another patch? > > It should apply to linux-next. It depends on two previous patches from > Peter Zijlstra in the sched/core branch of tip. See: > > https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=9397fa2ea3e7634f61da1ab76b9eb88ba04dfdfc > > and > > https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=e39acc37db34f6688e2c16e958fb1d662c422c81
Yeah, but the branch is tip/timers/core
Could you respin against it ?
Thanks
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