linux-kernel - Re: [PATCH v1 1/1] wq: Avoid using isolated cpus' timers on unbounded queue_delayed

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Message-ID: <Zbf8AVZaXwmExroX@LeoBras>
Date: Mon, 29 Jan 2024 16:26:57 -0300
From: Leonardo Bras <leobras@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: Leonardo Bras <leobras@...hat.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] wq: Avoid using isolated cpus' timers on unbounded queue_delayed_work

On Mon, Jan 29, 2024 at 08:18:15AM -1000, Tejun Heo wrote:
> Hello,
> 
> On Fri, Jan 26, 2024 at 07:05:35PM -0300, Leonardo Bras wrote:
> > > 	if (housekeeping_enabled(HK_TYPE_TIMER)) {
> > > 		cpu = smp_processor_id();
> > > 		if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
> > > 			cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
> > > 		add_timer_on(timer, cpu);
> > > 	} else {
> > > 		if (likely(cpu == WORK_CPU_UNBOUND))
> > > 			add_timer(timer, cpu);
> > > 		else
> > > 			add_timer_on(timer, cpu);
> > > 	}
> > > 
> > > Thanks.
> > 
> > I am not really against it, but for me it's kind of weird to have that many 
> > calls to add_timer_on() if we can avoid it. 
> > 
> > I would rather go with:
> > 
> > ###
> > if (unlikely(cpu != WORK_CPU_UNBOUND)) {
> > 	add_timer_on(timer, cpu);
> > 	return;
> > }
> > 
> > if (!housekeeping_enabled(HK_TYPE_TIMER)) {
> > 	add_timer(timer);
> > 	return;
> > }
> > 
> > cpu = smp_processor_id();
> > if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
> > 	cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
> > 
> > add_timer_on(timer, cpu);
> > ###
> > 
> > What do you think?
> 
> Isn't that still the same number of add_timer[_on]() calls?

Yeah, sorry about this, what I meant was: If we are ok on calling 
add_timer_on() multiple times, I would rather go with the above version, as 
I think it's better for readability.

> 
> Thanks.

Thank you for reviewing!
Leo

> 
> -- 
> tejun
>