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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72d405489fbsm59505b3a.24.2025.01.09.09.36.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jan 2025 09:36:18 -0800 (PST) Date: Thu, 9 Jan 2025 09:36:15 -0800 From: Joe Damato To: Magnus Karlsson Cc: Stanislav Fomichev , 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 Subject: Re: [PATCH net] xsk: Bring back busy polling support Message-ID: Mail-Followup-To: Joe Damato , Magnus Karlsson , Stanislav Fomichev , 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 References: <20250109003436.2829560-1-sdf@fomichev.me> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jan 09, 2025 at 04:22:16PM +0100, Magnus Karlsson wrote: > On Thu, 9 Jan 2025 at 01:35, 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. As a bonus, the > resulting code is much nicer too. > > I just took a look at the Intel drivers and some of our drivers have > not been converted to use netif_queue_set_napi() yet. Just ice, e1000, > and e1000e use it. But that is on us to fix. igc also supports it ;) I tried to add support to i40e some time ago, but ran into some issues and didn't hear back, so I gave up on i40e. In case my previous attempt is helpful for anyone at Intel, see [1]. [1]: https://lore.kernel.org/lkml/20240410043936.206169-1-jdamato@fastly.com/