Public bug reported:
352ccf890a3e91f58bc32503f9afdc161bc2c34a
-------------------------
KVM: s390: improve interrupt cpu for wakeup
Turns out that picking an idle CPU for floating interrupts has
some
negative side effects. The guest will keep the IO workload on its
CPU
and rather use an IPI from the interrupt CPU instead of moving
workload.
For example a guest with 2 vCPUs and 1 fio process might run that
fio on
vcpu1. If after diag500 both vCPUs are idle then vcpu0 is woken
up. The
guest will then do an IPI from vcpu0 to vcpu1.
So lets change the heuristics and prefer the last CPU that went to
sleep. This one is likely still in halt polling and can be woken
up
quickly.
This patch shows significant improvements in terms of bandwidth or
cpu consumption for fio and uperf workloads and seems to be a net
win.
Link:
https://lore.kernel.org/linux-s390/[email protected]/
Reviewed-by: Christoph Schlameu? <[email protected]>
Signed-off-by: Christian Borntraeger <[email protected]>
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-216078 severity-high
targetmilestone-inin---
** Tags added: architecture-s39064 bugnameltc-216078 severity-high
targetmilestone-inin---
** Changed in: ubuntu
Assignee: (unassigned) => Skipper Bug Screeners (skipper-screen-team)
** Package changed: ubuntu => linux (Ubuntu)
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https://bugs.launchpad.net/bugs/2132317
Title:
[UBUNTU 24.04] KVM: s390: improve interrupt cpu for wakeup
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