From: Joe Damato <jdamato@fastly.com>
To: Stanislav Fomichev <sdf@fomichev.me>
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, horms@kernel.org, ast@kernel.org,
daniel@iogearbox.net, hawk@kernel.org, john.fastabend@gmail.com,
bjorn@kernel.org, magnus.karlsson@intel.com,
maciej.fijalkowski@intel.com, jonathan.lemon@gmail.com,
mkarsten@uwaterloo.ca, alazar@nvidia.com
Subject: Re: [PATCH net] xsk: Bring back busy polling support
Date: Thu, 9 Jan 2025 09:32:09 -0800 [thread overview]
Message-ID: <Z4AIGWGVrEfk1yvE@LQ3V64L9R2> (raw)
In-Reply-To: <20250109003436.2829560-1-sdf@fomichev.me>
On Wed, Jan 08, 2025 at 04:34:36PM -0800, Stanislav Fomichev wrote:
> Commit 86e25f40aa1e ("net: napi: Add napi_config") moved napi->napi_id
> assignment to a later point in time (napi_hash_add_with_id). This breaks
> __xdp_rxq_info_reg which copies napi_id at an earlier time and now
> stores 0 napi_id. It also makes sk_mark_napi_id_once_xdp and
> __sk_mark_napi_id_once useless because they now work against 0 napi_id.
> Since sk_busy_loop requires valid napi_id to busy-poll on, there is no way
> to busy-poll AF_XDP sockets anymore.
>
> Bring back the ability to busy-poll on XSK by resolving socket's napi_id
> at bind time. This relies on relatively recent netif_queue_set_napi,
> but (assume) at this point most popular drivers should have been converted.
> This also removes per-tx/rx cycles which used to check and/or set
> the napi_id value.
>
> Confirmed by running a busy-polling AF_XDP socket
> (github.com/fomichev/xskrtt) on mlx5 and looking at BusyPollRxPackets
> from /proc/net/netstat.
Thanks Stanislav for finding and fixing this.
I've CC'd Alex who reported a bug a couple weeks ago that might be
fixed by this change.
Alex: would you mind applying this patch to your tree to see if this
solves the issue you reported [1] ?
[1]: https://lore.kernel.org/netdev/DM8PR12MB5447837576EA58F490D6D4BFAD052@DM8PR12MB5447.namprd12.prod.outlook.com/
next prev parent reply other threads:[~2025-01-09 17:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-09 0:34 [PATCH net] xsk: Bring back busy polling support Stanislav Fomichev
2025-01-09 15:22 ` Magnus Karlsson
2025-01-09 16:43 ` Jakub Kicinski
2025-01-09 17:36 ` Joe Damato
2025-01-09 17:32 ` Joe Damato [this message]
2025-01-11 2:20 ` patchwork-bot+netdevbpf
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