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---Problem Description---
There can be rcu stalls when running lots of large guests with storage keys:
[1377614.579833] rcu: INFO: rcu_sched self-detected stall on CPU
[1377614.579845] rcu: 18-....: (2099 ticks this GP)
idle=54e/1/0x4000000000000002 softirq=35598716/35598716 fqs=998
[1377614.579895] (t=2100 jiffies g=155867385 q=20879)
[1377614.579898] Task dump for CPU 18:
[1377614.579899] CPU 1/KVM R running task 0 1030947 256019
0x06000004
[1377614.579902] Call Trace:
[1377614.579912] ([<0000001f1f4b4f52>] show_stack+0x7a/0xc0)
[1377614.579918] [<0000001f1ec8e96c>] sched_show_task.part.0+0xdc/0x100
[1377614.579919] [<0000001f1f4b7248>] rcu_dump_cpu_stacks+0xc0/0x100
[1377614.579924] [<0000001f1ecdd10c>] rcu_sched_clock_irq+0x75c/0x980
[1377614.579926] [<0000001f1eceb26c>] update_process_times+0x3c/0x80
[1377614.579931] [<0000001f1ecfcfea>] tick_sched_handle.isra.0+0x4a/0x70
[1377614.579932] [<0000001f1ecfd28e>] tick_sched_timer+0x5e/0xc0
[1377614.579933] [<0000001f1ecec294>] __hrtimer_run_queues+0x114/0x2f0
[1377614.579935] [<0000001f1ececfdc>] hrtimer_interrupt+0x12c/0x2a0
[1377614.579938] [<0000001f1ebecb6a>] do_IRQ+0xaa/0xb0
[1377614.579942] [<0000001f1f4c6d08>] ext_int_handler+0x130/0x134
[1377614.579945] [<0000001f1ec0af10>] ptep_zap_key+0x40/0x60
Contact Information = cborn...@de.ibm.com
---uname output---
RELEASE: 5.4.0-90-generic
VERSION: #101-Ubuntu SMP Fri Oct 15 19:59:45 UTC 2021
== Comment: #1 - Christian Borntraeger <cborn...@de.ibm.com> - 2022-05-24
03:59:37 ==
This is a test patch that might address the rcu stalls.
== Comment: #2 - Christian Borntraeger <cborn...@de.ibm.com> - 2022-05-24
04:00:22 ==
This is a 2nd patch that reduces the cost of key setting.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-198360 severity-medium
targetmilestone-inin---
--
[UBUNTU 20.04] rcu stalls with many storage key guests
https://bugs.launchpad.net/bugs/1975582
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