linux-kernel - Re: [PATCH] sched_ext: improve WAKE_SYNC behavior for default idle CPU selection

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Message-ID: <ZxKdAvnLOmzPH4in@slm.duckdns.org>
Date: Fri, 18 Oct 2024 07:38:10 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <andrea.righi@...ux.dev>
Cc: David Vernet <void@...ifault.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: improve WAKE_SYNC behavior for default idle
 CPU selection

Hello,

On Fri, Oct 18, 2024 at 11:40:33AM +0200, Andrea Righi wrote:
...
> +	 * If WAKE_SYNC, try to migrate the wakee to the waker's CPU.
> +	 */
> +	if (wake_flags & SCX_WAKE_SYNC) {
> +		cpu = smp_processor_id();
> +
> +		/*
> +		 * If the waker's CPU is cache affine and prev_cpu is idle,
> +		 * then avoid a migration.
> +		 */
> +		if (cpus_share_cache(cpu, prev_cpu) &&
> +		    test_and_clear_cpu_idle(prev_cpu))
>  			goto cpu_found;

Shouldn't this do set cpu to prev_cpu before jumping to cpu_found?

Thanks.

-- 
tejun