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Message-ID: <5220E606.8010008@cogentembedded.com>
Date: Fri, 30 Aug 2013 22:35:50 +0400
From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To: Jason Wang <jasowang@...hat.com>
CC: mst@...hat.com, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 4/6] vhost_net: determine whether or not to use zerocopy
at one time
Hello.
On 08/30/2013 08:29 AM, Jason Wang wrote:
> Currently, even if the packet length is smaller than VHOST_GOODCOPY_LEN, if
> upend_idx != done_idx we still set zcopy_used to true and rollback this choice
> later. This could be avoided by determine zerocopy once by checking all
> conditions at one time before.
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
> drivers/vhost/net.c | 46 +++++++++++++++++++---------------------------
> 1 files changed, 19 insertions(+), 27 deletions(-)
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 8a6dd0d..ff60c2a 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -404,43 +404,35 @@ static void handle_tx(struct vhost_net *net)
> iov_length(nvq->hdr, s), hdr_size);
> break;
> }
> - zcopy_used = zcopy && (len >= VHOST_GOODCOPY_LEN ||
> - nvq->upend_idx != nvq->done_idx);
> +
> + zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
> + && (nvq->upend_idx + 1) % UIO_MAXIOV != nvq->done_idx
> + && vhost_net_tx_select_zcopy(net);
Could you leave && on a first of two lines, matching the previous style?
>
> /* use msg_control to pass vhost zerocopy ubuf info to skb */
> if (zcopy_used) {
> + struct ubuf_info *ubuf;
> + ubuf = nvq->ubuf_info + nvq->upend_idx;
> +
> vq->heads[nvq->upend_idx].id = head;
[...]
> + vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
> + ubuf->callback = vhost_zerocopy_callback;
> + ubuf->ctx = nvq->ubufs;
> + ubuf->desc = nvq->upend_idx;
> + msg.msg_control = ubuf;
> + msg.msg_controllen = sizeof(ubuf);
'sizeof(ubuf)' where 'ubuf' is a pointer? Are you sure it shouldn't be
'sizeof(*ubuf)'?
WBR, Sergei
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