netdev - Re: [PATCH net-next 09/11] tuntap: accept an array of XDP buffs through sendmsg()

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Date:   Fri, 7 Sep 2018 15:33:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 09/11] tuntap: accept an array of XDP buffs
 through sendmsg()



On 2018年09月07日 01:51, Michael S. Tsirkin wrote:
> On Thu, Sep 06, 2018 at 12:05:24PM +0800, Jason Wang wrote:
>> This patch implement TUN_MSG_PTR msg_control type. This type allows
>> the caller to pass an array of XDP buffs to tuntap through ptr field
>> of the tun_msg_control. If an XDP program is attached, tuntap can run
>> XDP program directly. If not, tuntap will build skb and do a fast
>> receiving since part of the work has been done by vhost_net.
>>
>> This will avoid lots of indirect calls thus improves the icache
>> utilization and allows to do XDP batched flushing when doing XDP
>> redirection.
>>
>> Signed-off-by: Jason Wang<jasowang@...hat.com>
> Is most of the benefit in batched flushing or skipping
> indirect calls? Because if it's flushing we can gain
> most of it easily by adding an analog of xmit_more.
>

Should be both. XDP_DROP doesn't flush but it gives obvious improvement.

Thanks