linux-kernel - Re: [PATCH 0/9] qspinlock stuff -v15

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Message-ID: <55197D3B.4020701@hp.com>
Date:	Mon, 30 Mar 2015 12:43:39 -0400
From:	Waiman Long <waiman.long@...com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, paolo.bonzini@...il.com,
	boris.ostrovsky@...cle.com, paulmck@...ux.vnet.ibm.com,
	riel@...hat.com, torvalds@...ux-foundation.org,
	raghavendra.kt@...ux.vnet.ibm.com, david.vrabel@...rix.com,
	oleg@...hat.com, scott.norton@...com, doug.hatch@...com,
	linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	xen-devel@...ts.xenproject.org, kvm@...r.kernel.org,
	luto@...capital.net
Subject: Re: [PATCH 0/9] qspinlock stuff -v15

On 03/30/2015 12:29 PM, Peter Zijlstra wrote:
> On Mon, Mar 30, 2015 at 12:25:12PM -0400, Waiman Long wrote:
>> I did it differently in my PV portion of the qspinlock patch. Instead of
>> just waking up the CPU, the new lock holder will check if the new queue head
>> has been halted. If so, it will set the slowpath flag for the halted queue
>> head in the lock so as to wake it up at unlock time. This should eliminate
>> your concern of dong twice as many VMEXIT in an overcommitted scenario.
> We can still do that on top of all this right? As you might have
> realized I'm a fan of gradual complexity :-)

Of course. I am just saying that the concern can be addressed with some 
additional code change.

-Longman
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