linux-kernel - Re: [PATCH v9 00/13] support "task_isolation" mode for nohz

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Message-ID: <5696BF7C.2080800@ezchip.com>
Date:	Wed, 13 Jan 2016 16:19:56 -0500
From:	Chris Metcalf <cmetcalf@...hip.com>
To:	Ingo Molnar <mingo@...nel.org>, Mark Rutland <mark.rutland@....com>
CC:	Will Deacon <will.deacon@....com>,
	Gilad Ben Yossef <giladb@...hip.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Andy Lutomirski <luto@...capital.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	<linux-doc@...r.kernel.org>, <linux-api@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 00/13] support "task_isolation" mode for nohz_full

On 01/13/2016 05:44 AM, Ingo Molnar wrote:
> * Chris Metcalf <cmetcalf@...hip.com> wrote:
>
>> (Adding Mark to cc's)
>>
>> On 01/12/2016 05:07 AM, Will Deacon wrote:
>>> On Mon, Jan 11, 2016 at 04:15:50PM -0500, Chris Metcalf wrote:
>>>> Ping!  There has been no substantive feedback to this version of
>>>> the patch in the week since I posted it, which optimistically suggests
>>>> to me that people may be satisfied with it.  If that's true, Frederic,
>>>> I assume this would be pulled into your tree?
>>>>
>>>> I have slightly updated the v9 patch series since this posting:
>>>>
>>>> [...]
>>>>
>>>> - Incorporated Mark Rutland's changes to convert arm64
>>>>    assembly to C code instead of using my own version.
>>> Please avoid queuing these patches -- the first is already in the arm64
>>> queue for 4.5 and the second was found to introduce a substantial
>>> performance regression on the syscall entry/exit path. I think Mark had
>>> an updated version to address that, so it would be easier not to have
>>> an old version sitting in some other queue!
>> I am not formally queueing them anywhere (like linux-next), though
>> now that you mention it, that's a pretty good idea - I'll talk to Steven
>> about that, assuming this merge window closes without the task
>> isolation stuff going in.
> NAK. Given the controversy, no way should this stuff go outside the primary trees
> it affects: the scheduler, timer, irq, etc. trees.

Fair enough.  I'll plan to do v10 once the merge window closes.

Mark, let me know when/if you get a new version of the de-asm stuff
for do_notify_resume() - thanks.  Or, would it be helpful if I worked up
the option I suggested, where we check the thread_info flags in the
assembly code before calling out to the new loop in do_notify_resume()?

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com