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[2a0c:4d80:42:443::2]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6433a3f8eb0sm1495033a12.12.2025.11.13.05.16.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Nov 2025 05:16:37 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 8CE6B329799; Thu, 13 Nov 2025 14:16:36 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Tariq Toukan , Tariq Toukan , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Andrew Lunn , "David S. Miller" Cc: Saeed Mahameed , Leon Romanovsky , Mark Bloch , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , netdev@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Gal Pressman , Leon Romanovsky , Moshe Shemesh , William Tu , Dragos Tatulea , Nimrod Oren , Alex Lazar Subject: Re: [PATCH net-next 0/6] net/mlx5e: Speedup channel configuration operations In-Reply-To: <60c0b805-92e9-48c0-a4dc-5ea071728b3d@gmail.com> References: <1762939749-1165658-1-git-send-email-tariqt@nvidia.com> <874iqzldvq.fsf@toke.dk> <89e33ec4-051d-4ca5-8fcd-f500362dee91@gmail.com> <87ms4rjjm0.fsf@toke.dk> <60c0b805-92e9-48c0-a4dc-5ea071728b3d@gmail.com> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 13 Nov 2025 14:16:36 +0100 Message-ID: <878qgajcnf.fsf@toke.dk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Tariq Toukan writes: > On 12/11/2025 18:33, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> Tariq Toukan writes: >>=20 >>> On 12/11/2025 12:54, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >>>> Tariq Toukan writes: >>>> >>>>> Hi, >>>>> >>>>> This series significantly improves the latency of channel configurati= on >>>>> operations, like interface up (create channels), interface down (dest= roy >>>>> channels), and channels reconfiguration (create new set, destroy old >>>>> one). >>>> >>>> On the topic of improving ifup/ifdown times, I noticed at some point >>>> that mlx5 will call synchronize_net() once for every queue when they a= re >>>> deactivated (in mlx5e_deactivate_txqsq()). Have you considered changing >>>> that to amortise the sync latency over the full interface bringdown? :) >>>> >>>> -Toke >>>> >>>> >>> >>> Correct! >>> This can be improved and I actually have WIP patches for this, as I'm >>> revisiting this code area recently. >>=20 >> Excellent! We ran into some issues with this a while back, so would be >> great to see this improved. >>=20 >> -Toke >>=20 > > Can you elaborate on the test case and issues encountered? > To make sure I'm addressing them. Sure, thanks for taking a look! The high-level issue we've been seeing involves long delays creating and tearing down OpenShift (Kubernetes) pods that have SR-IOV devices assigned to them. The worst example of involved a test that basically reboots an application (tearing down its pods and immediately recreating them), which takes up to ~10 minutes for ~100 pods. Because a lot of the wait happens with the RNTL held, we also get cascading errors to other parts of the system. This is how I ended up digging into what the mlx5 driver was doing while holding the RTNL, which is where I noticed the "synchronize_net() in a loop" behaviour. We're working on reducing the blast radius of the RTNL in general, but the setup/teardown time seems to be driver specific, so any improvements here would be welcome, I guess :) -Toke