Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods
To: Peter Zijlstra <peterz@infradead.org>, Aubrey Li <aubrey.li@intel.com>
Cc: tglx@linutronix.de, len.brown@intel.com, rjw@rjwysocki.net,
        ak@linux.intel.com, tim.c.chen@linux.intel.com, arjan@linux.intel.com,
        paulmck@linux.vnet.ibm.com, yang.zhang.wz@gmail.com, x86@kernel.org,
        linux-kernel@vger.kernel.org
References: <1499650721-5928-1-git-send-email-aubrey.li@intel.com>
 <20170710084647.zs6wkl3fumszd33g@hirez.programming.kicks-ass.net>
From: "Li, Aubrey" <aubrey.li@linux.intel.com>
Message-ID: <598f0c65-6b3d-8562-6b8a-8edb508b0b00@linux.intel.com>
Date: Mon, 10 Jul 2017 21:59:41 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.1
MIME-Version: 1.0
In-Reply-To: <20170710084647.zs6wkl3fumszd33g@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 742
Lines: 21

On 2017/7/10 16:46, Peter Zijlstra wrote:
> On Mon, Jul 10, 2017 at 09:38:30AM +0800, Aubrey Li wrote:
>> We measured 3%~5% improvemnt in disk IO workload, and 8%~20% improvement in
>> network workload. 
> 
> Argh, what a mess :/
> 
> So how much of the gain is simply due to skipping NOHZ?

netperf reports 6~7% improvement due to skipping NOHZ, but still have 2~3% 
improvement due to excluding RCU idle enter/exit, c-state selection and other
deferrable items. Also a shallow HW c-state is used in the idle loop, which
means faster HW sleep enter and exit.

> Mike used to carry a patch that would throttle NOHZ. And that is a _far_ small
> and simpler patch to do.
> 
Can you please point me to the link of Mike's patch?

Thanks,
-Aubrey