Re: [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path

From: Quan Xu <quan.xu0@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>,
	Len Brown <len.brown@intel.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org,
	LKML <linux-kernel@vger.kernel.org>,
	virtualization@lists.linux-foundation.org,
	Kyle Huey <me@kylehuey.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, Quan Xu <quan.xu03@gmail.com>,
	Andy Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Tobias Klauser <tklauser@distanz.ch>
Subject: Re: [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path
Date: Thu, 16 Nov 2017 17:29:58 +0800	[thread overview]
Message-ID: <13a3a5c5-ec14-131f-fe6a-01700783de81__28585.7426621535$1511414921$gmane$org@gmail.com> (raw)
In-Reply-To: <20171116084555.it2hqajxxd6ld5tq@hirez.programming.kicks-ass.net>

On 2017-11-16 16:45, Peter Zijlstra wrote:
> On Wed, Nov 15, 2017 at 11:03:08PM +0100, Thomas Gleixner wrote:
>> If I understand the problem correctly then he wants to avoid the heavy
>> lifting in tick_nohz_idle_enter() in the first place, but there is already
>> an interesting quirk there which makes it exit early.
> Sure. And there are people who want to do the same for native.
>
> Adding more ugly and special cases just isn't the way to go about doing
> that.
>
> I'm fairly sure I've told the various groups that want to tinker with
> this to work together on this. I've also in fairly significant detail
> sketched how to rework the idle code and idle predictors.
>
> At this point I'm too tired to dig any of that up, so I'll just keep
> saying no to patches that don't even attempt to go in the right
> direction.
Peter, take care.

I really have considered this factor, and try my best not to interfere 
with scheduler/idle code.
if irq_timings code is ready, I can use it directly. I think irq_timings 
is not an easy task, I'd
like to help as much as I can.  Also don't try to touch tick_nohz* code 
again.

as tglx suggested, this can be handled either in a HV specific idle driver or even in the generic core code.

I hope this is in the right direction.

Quan
Alibaba Cloud

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