netdev - Re: [PATCH 2/6] vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal

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Message-ID: <5212D564.80200@redhat.com>
Date:	Tue, 20 Aug 2013 10:33:08 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] vhost_net: use vhost_add_used_and_signal_n() in vhost_zerocopy_signal_used()

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 <jasowang@...hat.com>
> 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.
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