# Re: \[PATCH 2/6\] vhost\_net: use vhost\_add\_used\_and\_signal\_n() in vhost\_zerocopy\_signal\_used()

- From: Jason Wang \<hidden\>
- Date: 2013-08-20 02:33:14 
- List: netdev
- Page: https://ratatoskr.run/netdev/2013/08/4103409
- Thread: https://ratatoskr.run/kvm/2013/08/4101775/t.md

```text
On 08/16/2013 05:54 PM, Michael S. Tsirkin wrote:
> On Fri, Aug 16, 2013 at 01:16:26PM +0800, Jason Wang wrote:
>> > Switch to use vhost_add_used_and_signal_n() to avoid multiple calls to
>> > vhost_add_used_and_signal(). With the patch we will call at most 2 times
>> > (consider done_idx warp around) compared to N times w/o this patch.
>> > 
>> > Signed-off-by: Jason Wang <redacted>
> So? Does this help performance then?
>

Looks like it can especially when guest does support event index. When
guest enable tx interrupt, this can saves us some unnecessary signal to
guest. I will do some test.
```