h-prod does not function across cores
Bug #1670726 reported by
bugproxy
This bug affects 1 person
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Undecided
|
Unassigned | ||
Yakkety |
Fix Released
|
Undecided
|
Tim Gardner | ||
Zesty |
Fix Released
|
Undecided
|
Unassigned |
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.
tags: | added: architecture-ppc64le bugnameltc-152309 severity-high targetmilestone-inin16042 |
Changed in ubuntu: | |
assignee: | nobody → Taco Screen team (taco-screen-team) |
affects: | ubuntu → linux (Ubuntu) |
Changed in linux (Ubuntu Yakkety): | |
status: | In Progress → Fix Committed |
tags: |
added: verification-done-yakkety removed: verification-needed-yakkety |
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Leann,
A kernel patch request from IBM.
On 03/07/2017 07:29 AM, Launchpad Bug Tracker wrote: ppc64le bugnameltc-152309 severity-high targetmilestone -inin16042
> bugproxy (bugproxy) has assigned this bug to you for Ubuntu:
>
> 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: ubuntu
> Importance: Undecided
> Assignee: Taco Screen team (taco-screen-team)
> Status: New
>
>
> ** Tags: architecture-
--
Michael Hohnbaum
OIL Program Manager
Power (ppc64el) Development Project Manager
Canonical, Ltd.