From: "Björn Töpel" <bjorn.topel@intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
"Björn Töpel" <bjorn.topel@gmail.com>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
magnus.karlsson@intel.com, ast@kernel.org, daniel@iogearbox.net,
maciej.fijalkowski@intel.com, sridhar.samudrala@intel.com,
jesse.brandeburg@intel.com, qi.z.zhang@intel.com,
kuba@kernel.org, edumazet@google.com, jonathan.lemon@gmail.com,
maximmi@nvidia.com, intel-wired-lan@lists.osuosl.org,
netanel@amazon.com, akiyano@amazon.com,
michael.chan@broadcom.com, sgoutham@marvell.com,
ioana.ciornei@nxp.com, ruxandra.radulescu@nxp.com,
thomas.petazzoni@bootlin.com, mcroce@microsoft.com,
saeedm@nvidia.com, tariqt@nvidia.com, aelior@marvell.com,
ecree@solarflare.com, ilias.apalodimas@linaro.org,
grygorii.strashko@ti.com, sthemmin@microsoft.com,
kda@linux-powerpc.org
Subject: Re: [PATCH bpf-next v2 06/10] xsk: propagate napi_id to XDP socket Rx path
Date: Mon, 16 Nov 2020 13:01:40 +0100 [thread overview]
Message-ID: <614a7ce4-2b6b-129b-de7d-71428f7a71f6@intel.com> (raw)
In-Reply-To: <20201116064953-mutt-send-email-mst@kernel.org>
On 2020-11-16 12:55, Michael S. Tsirkin wrote:
> On Mon, Nov 16, 2020 at 12:04:12PM +0100, Björn Töpel wrote:
>> From: Björn Töpel <bjorn.topel@intel.com>
>>
>> Add napi_id to the xdp_rxq_info structure, and make sure the XDP
>> socket pick up the napi_id in the Rx path. The napi_id is used to find
>> the corresponding NAPI structure for socket busy polling.
>>
>> Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
>> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
>
> A bunch of drivers just pass in 0. could you explain when
> is that ok? how bad is it if the wrong id is used?
>
If zero is passed, which is a non-valid NAPI_ID, busy-polling will never
be performed.
Depending on the structure of the driver, napi might or might not be
initialized (napi_id != 0) or even available. When it wasn't obvious, I
simply set it to zero.
So, short; No harm if zero, but busy-polling cannot be used in an XDP
context.
[...]
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 21b71148c532..d71fe41595b7 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1485,7 +1485,7 @@ static int virtnet_open(struct net_device *dev)
>> if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
>> schedule_delayed_work(&vi->refill, 0);
>>
>> - err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i);
>> + err = xdp_rxq_info_reg(&vi->rq[i].xdp_rxq, dev, i, 0);
>> if (err < 0)
>> return err;
>>
>
> Should this be rq.napi.napi_id ?
>
Yes, if rq.napi.napi_id is valid here! Is it?
Cheers,
Björn
next prev parent reply other threads:[~2020-11-16 12:38 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 11:04 [PATCH bpf-next v2 00/10] Introduce preferred busy-polling Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 01/10] net: introduce " Björn Töpel
2020-11-16 16:04 ` Jakub Kicinski
2020-11-16 16:19 ` Björn Töpel
2020-11-16 17:28 ` Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 02/10] net: add SO_BUSY_POLL_BUDGET socket option Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 03/10] xsk: add support for recvmsg() Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 04/10] xsk: check need wakeup flag in sendmsg() Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 05/10] xsk: add busy-poll support for {recv,send}msg() Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 06/10] xsk: propagate napi_id to XDP socket Rx path Björn Töpel
2020-11-16 11:19 ` Tariq Toukan
2020-11-16 11:55 ` Michael S. Tsirkin
2020-11-16 12:01 ` Björn Töpel [this message]
2020-11-16 12:42 ` Michael S. Tsirkin
2020-11-16 13:24 ` Björn Töpel
2020-11-16 13:55 ` Michael S. Tsirkin
2020-11-16 17:40 ` Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 07/10] samples/bpf: use recvfrom() in xdpsock/rxdrop Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 08/10] samples/bpf: use recvfrom() in xdpsock/l2fwd Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 09/10] samples/bpf: add busy-poll support to xdpsock Björn Töpel
2020-11-16 11:04 ` [PATCH bpf-next v2 10/10] samples/bpf: add option to set the busy-poll budget Björn Töpel
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