Public bug reported:
There is a performance problem issue with h-prod. I can see that h-prod
calls are only waking hardware threads from a h-cede call when the
caller is on the same core as the thread being awoken (sibling theads).
For cross core prods the target thread remains in h-cede until its next
decrementer interrupt. That is causing guest OS some significant
dispatching delays.
The fix is now upstream as commit 8464c8842de2 ("KVM: PPC: Book3S HV:
Fix H_PROD to actually wake the target vcpu", 2016-12-06) in v4.11-rc1.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Taco Screen team (taco-screen-team)
Status: New
** Tags: architecture-ppc64le bugnameltc-152309 severity-high
targetmilestone-inin16042
** Tags added: architecture-ppc64le bugnameltc-152309 severity-high
targetmilestone-inin16042
** Changed in: ubuntu
Assignee: (unassigned) => Taco Screen team (taco-screen-team)
** Package changed: ubuntu => linux (Ubuntu)
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https://bugs.launchpad.net/bugs/1670726
Title:
h-prod does not function across cores
Status in linux package in Ubuntu:
New
Bug description:
There is a performance problem issue with h-prod. I can see that
h-prod calls are only waking hardware threads from a h-cede call when
the caller is on the same core as the thread being awoken (sibling
theads). For cross core prods the target thread remains in h-cede
until its next decrementer interrupt. That is causing guest OS some
significant dispatching delays.
The fix is now upstream as commit 8464c8842de2 ("KVM: PPC: Book3S HV:
Fix H_PROD to actually wake the target vcpu", 2016-12-06) in
v4.11-rc1.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1670726/+subscriptions
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