On Tue, 14 Feb 2023 16:06:26 +0000, Usama Arif <usama.arif@xxxxxxxxxxxxx> wrote: > > > > On 17/01/2023 10:29, Usama Arif wrote: > > This patchset adds support for vcpu_is_preempted in arm64, which allows the guest > > to check if a vcpu was scheduled out, which is useful to know incase it was > > holding a lock. vcpu_is_preempted is well integrated in core kernel code and can > > be used to improve performance in locking (owner_on_cpu usage in mutex_spin_on_owner, > > mutex_can_spin_on_owner, rtmutex_spin_on_owner and osq_lock) and scheduling > > (available_idle_cpu which is used in several places in kernel/sched/fair.c > > for e.g. in wake_affine to determine which CPU can run soonest). > > > > This patchset shows significant improvement on overcommitted hosts (vCPUs > pCPUS), > > as waiting for preempted vCPUs reduces performance. > > > > Hi, > > Just wanted to check if there are any comments for this? Not a lot, I'm afraid. My concerns with this thing are still the same: - it is KVM-specific - it doesn't work with nested virtualisation - its correctness is unproven on arm64 I'm also not going to entertain any of this without the core arm64 maintainers saying that they will enable this. Thanks, M. -- Without deviation from the norm, progress is not possible.
