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a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=jiCTI4zE5U7BLdzWsZGv:22 a=3I1J8UUJPc9JN9BFgKH3:22 a=x44POAVFR4TL_THfJn8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: c1Aj3caNtlePCMRWmEJ9PHv6-J8wM_Xv X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTIxMDA5MSBTYWx0ZWRfX5/PNePRRk1Sx asmthYZA0q/N5hLPX5xdAcnMywXh7LHMNAMsjpZEIcgBWQYPstfPMBRFM4Djf6ei7xpNv1V3tGf 40dwA1zp+T3aRcQE1Wa3qTNs1QJt5UXUClRigrgiBBi24Q3Ry0mHnUiCP2qBhIZkJBV6ke5K8I8 /A/P+hTBN996E+9aJhDDY7WWTm/A7RUCAWVEubVdPyqiDwhL1azDDhverIkHH5NxL2o9kDwYeuQ hE94H4UtFaMiWOZDi4L5JOMXMVnH3YJZi0OyMX/bRkGaFgzcX7rXrrmsOYbA2zOcm2UF3aUfYoC lPpureNOy4G10SB4wYghmdohK7fs+cjb7Yj+pGduY5lZFAoc4SuhtRT16fbmxXpWcQUBR9Se/v6 UTiQ1EFlKigTqT8ho4wDw6I91gHZTNqMKO5dbgNekm55ytnUwMnp0Odh0G251eD5sBPUZh1FhNr rObKcDYHaPgBWMxUMcg== X-Proofpoint-GUID: c1Aj3caNtlePCMRWmEJ9PHv6-J8wM_Xv On 2026-05-15 12:19 PM, Sean Christopherson wrote: > Prefer the TSC over kvmclock for sched_clock if the TSC is constant, > nonstop, and not marked unstable via command line. I.e. use the same > criteria as tweaking the clocksource rating so that TSC is preferred over > kvmclock. Per the below comment from native_sched_clock(), sched_clock > is more tolerant of slop than clocksource; using TSC for clocksource but > not sched_clock makes little to no sense, especially now that KVM CoCo > guests with a trusted TSC use TSC, not kvmclock. > > /* > * Fall back to jiffies if there's no TSC available: > * ( But note that we still use it if the TSC is marked > * unstable. We do this because unlike Time Of Day, > * the scheduler clock tolerates small errors and it's > * very important for it to be as fast as the platform > * can achieve it. ) > */ > > The only advantage of using kvmclock is that doing so allows for early > and common detection of PVCLOCK_GUEST_STOPPED, but that code has been > broken for over two years with nary a complaint, i.e. it can't be > _that_ valuable. And as above, certain types of KVM guests are losing > the functionality regardless, i.e. acknowledging PVCLOCK_GUEST_STOPPED > needs to be decoupled from sched_clock() no matter what. Has it been broken for two years because of pvclock_clocksource_read_nowd()? Thank you very much! Dongli Zhang