From: "Toke Høiland-Jørgensen" <toke@redhat•com>
To: Toshiaki Makita <makita.toshiaki@lab•ntt.co.jp>,
Alexei Starovoitov <ast@kernel•org>,
Daniel Borkmann <daniel@iogearbox•net>,
"David S. Miller" <davem@davemloft•net>,
Jakub Kicinski <jakub.kicinski@netronome•com>,
Jesper Dangaard Brouer <hawk@kernel•org>,
John Fastabend <john.fastabend@gmail•com>
Cc: netdev@vger•kernel.org, xdp-newbies@vger•kernel.org, bpf@vger•kernel.org
Subject: Re: [PATCH bpf-next 1/3] xdp: Add bulk XDP_TX queue
Date: Thu, 23 May 2019 13:33:54 +0200 [thread overview]
Message-ID: <87v9y11k2l.fsf@toke.dk> (raw)
In-Reply-To: <2ab04d02-634e-9420-9514-e4ede08bcb10@lab.ntt.co.jp>
Toshiaki Makita <makita.toshiaki@lab•ntt.co.jp> writes:
> On 2019/05/23 20:11, Toke Høiland-Jørgensen wrote:
>> Toshiaki Makita <makita.toshiaki@lab•ntt.co.jp> writes:
>>
>>> XDP_TX is similar to XDP_REDIRECT as it essentially redirects packets to
>>> the device itself. XDP_REDIRECT has bulk transmit mechanism to avoid the
>>> heavy cost of indirect call but it also reduces lock acquisition on the
>>> destination device that needs locks like veth and tun.
>>>
>>> XDP_TX does not use indirect calls but drivers which require locks can
>>> benefit from the bulk transmit for XDP_TX as well.
>>
>> XDP_TX happens on the same device, so there's an implicit bulking
>> happening because of the NAPI cycle. So why is an additional mechanism
>> needed (in the general case)?
>
> Not sure what the implicit bulking you mention is. XDP_TX calls
> .ndo_xdp_xmit() for each packet, and it acquires a lock in veth and
> tun. To avoid this, we need additional storage for bulking like devmap
> for XDP_REDIRECT.
The bulking is in veth_poll(), where veth_xdp_flush() is only called at
the end. But see my other reply to the veth.c patch for the lock
contention issue...
-Toke
next prev parent reply other threads:[~2019-05-23 11:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-23 10:56 [PATCH bpf-next 0/3] veth: Bulk XDP_TX Toshiaki Makita
2019-05-23 10:56 ` [PATCH bpf-next 1/3] xdp: Add bulk XDP_TX queue Toshiaki Makita
2019-05-23 11:11 ` Toke Høiland-Jørgensen
2019-05-23 11:24 ` Toshiaki Makita
2019-05-23 11:33 ` Toke Høiland-Jørgensen [this message]
2019-05-23 10:56 ` [PATCH bpf-next 2/3] xdp: Add tracepoint for bulk XDP_TX Toshiaki Makita
2019-05-23 13:12 ` Jesper Dangaard Brouer
2019-05-24 1:33 ` Toshiaki Makita
2019-05-23 10:56 ` [PATCH bpf-next 3/3] veth: Support " Toshiaki Makita
2019-05-23 11:25 ` Toke Høiland-Jørgensen
2019-05-23 11:35 ` Toshiaki Makita
2019-05-23 12:18 ` Toke Høiland-Jørgensen
2019-05-23 13:40 ` Toshiaki Makita
2019-05-23 13:29 ` Jesper Dangaard Brouer
2019-05-23 13:51 ` Toshiaki Makita
2019-05-24 3:13 ` Jason Wang
2019-05-24 3:28 ` Toshiaki Makita
2019-05-24 3:54 ` Jason Wang
2019-05-24 4:52 ` Toshiaki Makita
2019-05-24 9:53 ` Jesper Dangaard Brouer
2019-05-27 6:08 ` Toshiaki Makita
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