Re: [PATCH 0/2] net: Use synchronous wakeups selectively

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 14 Jul 2026 07:09:41 +0530 Srikar Dronamraju wrote:
> The scheduler assumes in several wakeup paths that a task using WF_SYNC
> is likely to yield the CPU shortly. However several networking wakeup
> paths unconditionally use synchronous wakeups even when the waking task
> continues execution.
> 
> During wakeup, with WF_SYNC flag set, because of the assumption that
> current thread is ready to give up, the wakee thread will be migrated
> from any core within the chip to the current LLC. If these operations
> are frequent, and wakers are actually not going away, then it will lead
> to load imbalance and hurt performance. This is especially true in
> architectures where LLCs are small and number of LLCs per chip are more.
> 
> Running vllm workload was run on Power10 system
>                                   No patch      with patch %diff
> Inference Time (sec)              17.84         16.35     -8.35%
> llm query bandwidth (tokens/sec)  14.78         16.21     +9.68%
> 
> Lower inference time and higher tokens/sec is better.

Somewhat related recent patch:

https://lore.kernel.org/all/20260708133815.3419465-1-usama.arif@linux.dev/

Maybe other maintainers will chime in, but I'm not convinced 
by the heuristics you're adding. The behavior will be workload
specific. The extent of networking involvement should be letting
the scheduler know that we're waking from IO, not leaking scheduler
heuristics into networking.
-- 
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