Re: [PATCH] sched/idle: Stop the tick when no cpuidle driver is available

[Thorsten Leemhuis <regressions@leemhuis.info>]

On 11/6/26 00:59, Florian Fainelli wrote:
> On 7/28/26 09:37, Christian Loehle wrote:
>> Commit f4c31b07b136 ("sched: idle: Consolidate the handling of two
>> special cases") changed the no-cpuidle-driver path to use the previous
>> tick wakeup heuristic.
>>
>> Oracle reported a substantial sysbench regression on small OCI VM shapes
>> with no cpuidle driver available. Reverting the commit recovered the lost
>> performance.
>>
>> Restore the previous tick handling for the no-driver case while retaining
>> the heuristic for the single-state cpuidle case.
>>
>> Fixes: f4c31b07b136 ("sched: idle: Consolidate the handling of two
>> special cases")
> [...]
> 
> We also hit this issue after it got back ported into stable trees (5.15,
> 6.1, etc.) and this is seen during a network throughput test. 
FWIW, a fix for the above-mentioned commit recently hit mainline, so I
wonder if that might change anything:

96a494c9cfd8f4 ("sched/cputime: Don't account idle time twice after
dyntick-idle") [v7.4-rc1]
https://lore.kernel.org/all/20261005194010.168299-1-stian@itx.no/

Ciao, Thorsten