linux-kernel - RE: [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate process

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Date:   Wed, 18 Jan 2017 04:56:58 +0000
From:   "Li, Liang Z" <liang.z.li@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "virtio-dev@...ts.oasis-open.org" <virtio-dev@...ts.oasis-open.org>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "amit.shah@...hat.com" <amit.shah@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "cornelia.huck@...ibm.com" <cornelia.huck@...ibm.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "david@...hat.com" <david@...hat.com>,
        "aarcange@...hat.com" <aarcange@...hat.com>,
        "dgilbert@...hat.com" <dgilbert@...hat.com>,
        "quintela@...hat.com" <quintela@...hat.com>
Subject: RE: [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate
 process

> > -	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> > -	virtqueue_kick(vq);
> > +static void do_set_resp_bitmap(struct virtio_balloon *vb,
> > +		unsigned long base_pfn, int pages)
> >
> > -	/* When host has read buffer, this completes via balloon_ack */
> > -	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> > +{
> > +	__le64 *range = vb->resp_data + vb->resp_pos;
> >
> > +	if (pages > (1 << VIRTIO_BALLOON_NR_PFN_BITS)) {
> > +		/* when the length field can't contain pages, set it to 0 to
> 
> /*
>  * Multi-line
>  * comments
>  * should look like this.
>  */
> 
> Also, pls start sentences with an upper-case letter.
> 

Sorry for that.

> > +		 * indicate the actual length is in the next __le64;
> > +		 */
> 
> This is part of the interface so should be documented as such.
> 
> > +		*range = cpu_to_le64((base_pfn <<
> > +				VIRTIO_BALLOON_NR_PFN_BITS) | 0);
> > +		*(range + 1) = cpu_to_le64(pages);
> > +		vb->resp_pos += 2;
> 
> Pls use structs for this kind of stuff.

I am not sure if you mean to use 

struct  range {
 	__le64 pfn: 52;
	__le64 nr_page: 12
}
Instead of the shift operation?

I didn't use this way because I don't want to include 'virtio-balloon.h' in page_alloc.c,
or copy the define of this struct in page_alloc.c

Thanks!
Liang