linux-kernel - Re: [Xen-devel] [PATCH] xen: release lock occasionally during ballooning

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Message-ID: <55ACCA5E.9070100@citrix.com>
Date:	Mon, 20 Jul 2015 11:15:58 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<david.vrabel@...rix.com>, <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH] xen: release lock occasionally during ballooning

On 10/07/15 15:42, Juergen Gross wrote:
> When dom0 is being ballooned balloon_process() will hold the balloon
> mutex until it is finished. This will block e.g. creation of new
> domains as the device backends for the new domain need some
> autoballooned pages for the ring buffers.
> 
> Avoid this by releasing the balloon mutex from time to time during
> ballooning. Add a state variable to indicate one balloon_process()
> is active to avoid multiple balloon processes fighting for the mutex.

Is this state variable necessary? balloon_process() is a work item so
there should only be one instance of it running anyway, yes?

David
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