linux-kernel - Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

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Date:   Mon, 10 Jul 2017 21:59:41 +0800
From:   "Li, Aubrey" <aubrey.li@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Aubrey Li <aubrey.li@...el.com>
Cc:     tglx@...utronix.de, len.brown@...el.com, rjw@...ysocki.net,
        ak@...ux.intel.com, tim.c.chen@...ux.intel.com,
        arjan@...ux.intel.com, paulmck@...ux.vnet.ibm.com,
        yang.zhang.wz@...il.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

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