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

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Date:   Tue, 17 Jan 2017 21:15:45 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Liang Li <liang.z.li@...el.com>
Cc:     kvm@...r.kernel.org, virtio-dev@...ts.oasis-open.org,
        qemu-devel@...gnu.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, amit.shah@...hat.com,
        dave.hansen@...el.com, cornelia.huck@...ibm.com,
        pbonzini@...hat.com, david@...hat.com, aarcange@...hat.com,
        dgilbert@...hat.com, quintela@...hat.com
Subject: Re: [PATCH v6 kernel 3/5] virtio-balloon: speed up inflate/deflate
 process

On Wed, Dec 21, 2016 at 02:52:26PM +0800, Liang Li wrote:
>  
> -	/* We should always be able to add one buffer to an empty queue. */
> -	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.

> +		 * 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.

> +	} else {
> +		*range = (base_pfn << VIRTIO_BALLOON_NR_PFN_BITS) | pages;
> +		vb->resp_pos++;
> +	}
> +}