linux-kernel - Re: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate process

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Message-ID: <20160728003644-mutt-send-email-mst@kernel.org>
Date:	Thu, 28 Jul 2016 00:39:14 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	Liang Li <liang.z.li@...el.com>, linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
	virtio-dev@...ts.oasis-open.org, kvm@...r.kernel.org,
	qemu-devel@...gnu.org, dgilbert@...hat.com, quintela@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Amit Shah <amit.shah@...hat.com>
Subject: Re: [PATCH v2 repost 4/7] virtio-balloon: speed up inflate/deflate
 process

On Wed, Jul 27, 2016 at 09:03:21AM -0700, Dave Hansen wrote:
> On 07/26/2016 06:23 PM, Liang Li wrote:
> > +	vb->pfn_limit = VIRTIO_BALLOON_PFNS_LIMIT;
> > +	vb->pfn_limit = min(vb->pfn_limit, get_max_pfn());
> > +	vb->bmap_len = ALIGN(vb->pfn_limit, BITS_PER_LONG) /
> > +		 BITS_PER_BYTE + 2 * sizeof(unsigned long);
> > +	hdr_len = sizeof(struct balloon_bmap_hdr);
> > +	vb->bmap_hdr = kzalloc(hdr_len + vb->bmap_len, GFP_KERNEL);
> 
> This ends up doing a 1MB kmalloc() right?  That seems a _bit_ big.  How
> big was the pfn buffer before?


Yes I would limit this to 1G memory in a go, will result
in a 32KByte bitmap.

-- 
MST