From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Sent: Monday, June 19, 2023 9:58 AM > > On 19/06/2023 18:44, Michael Kelley (LINUX) wrote: > > From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> 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@xxxxxxxxxxxxx> > >> > >> 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 ? > Ah, OK. Just to confirm, you are saying that this patch would go through the tip/timers/core branch, which does *not* have Peter's patches. Resolving the merge conflict will be done within the tip branches. Yes, I'll respin for tip/timers/core. Michael
