Re: [REPORT] sched: ITMT + DELAY_DEQUEUE: woken task waits ~1 ms behind another task on the preferred CPU while allowed CPUs are idle

[Francesco Nigro <nigro.fra@gmail.com>]

On Wed, 2026-11-04 at 04:13 +0100, Mike Galbraith wrote:
> In your specific case, dunno.  In general, absolutely.

I checked with boost on too, on the same box and kernel. I ran
asym_min and tbench on CPUs 4-7, without SMT siblings, with clocks
pinned and boost off, and with boost on and the full frequency
range, DELAY_DEQUEUE on.

With boost on, 0.82-1.09 % of asym_min wakeups per run waited at
least 0.5 ms with ITMT on, and none with ITMT off.

tbench throughput was the same with ITMT on or off in every setting
(within 1 %), and so was the busy CPUs' clock (within 0.2 %).
According to these new runs, with boost on ITMT gives no throughput
advantage and still causes the long stalls.

As a side note, I agree about DELAY_DEQUEUE: disabling it reduced
tbench throughput at full load, with ITMT on or off.

Scripts and raw output:
https://github.com/franz1981/itmt-delay-dequeue-repro/tree/1400f15

Tool use as in the report.

Thanks,
Franz