Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux

From: Julien Grall <julien.grall@citrix.com>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>, <ian.campbell@citrix.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
	<linux-kernel@vger.kernel.org>,
	David Vrabel <david.vrabel@citrix.com>,
	<xen-devel@lists.xenproject.org>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux
Date: Mon, 10 Aug 2015 14:36:10 +0100	[thread overview]
Message-ID: <55C8A8CA.7070409@citrix.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1508101352370.11337@kaball.uk.xensource.com>

On 10/08/15 13:55, Stefano Stabellini wrote:
>> If your only concern is the size of the array, we could decrease the
>> number of frames by batch. Or allocation the variable once a boot time.
> 
> Yes, that is my only concern. Allocating only nr_pages new struct page*
> would be good enough I guess.

That would be even worst. We shouldn't allocate the array at every call,
but at boot time.

Note that frame_list is already a static variable use 64KB when 64KB
page is used. I guess this will be unlikely to remove that much frame in
a single batch. But I will keep this optimization for later.

Anyway, I'm wondering if we could re-use the lru field to link the page
when allocate them and retrieve in the second loop in order to avoid the
pages array.

Regards,

-- 
Julien Grall