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Tsirkin" To: Jason Wang Cc: Simon Schippers , willemdebruijn.kernel@gmail.com, eperezma@redhat.com, stephen@networkplumber.org, leiyang@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org Subject: Re: [PATCH net-next v5 0/8] TUN/TAP & vhost_net: netdev queue flow control to avoid ptr_ring tail drop Message-ID: <20250924034112-mutt-send-email-mst@kernel.org> References: <20250922221553.47802-1-simon.schippers@tu-dortmund.de> <20250924031105-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: hG1CQ8oFKzako-oEV1RpHPGDTtW_hfSjCzIt5xiogYY_1758699720 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Wed, Sep 24, 2025 at 03:33:08PM +0800, Jason Wang wrote: > On Wed, Sep 24, 2025 at 3:18 PM Michael S. Tsirkin wrote: > > > > On Tue, Sep 23, 2025 at 12:15:45AM +0200, Simon Schippers wrote: > > > This patch series deals with TUN, TAP and vhost_net which drop incoming > > > SKBs whenever their internal ptr_ring buffer is full. Instead, with this > > > patch series, the associated netdev queue is stopped before this happens. > > > This allows the connected qdisc to function correctly as reported by [1] > > > and improves application-layer performance, see our paper [2]. Meanwhile > > > the theoretical performance differs only slightly: > > > > > > About this whole approach. > > What if userspace is not consuming packets? > > Won't the watchdog warnings appear? > > Is it safe to allow userspace to block a tx queue > > indefinitely? > > I think it's safe as it's a userspace device, there's no way to > guarantee the userspace can process the packet in time (so no watchdog > for TUN). > > Thanks Hmm. Anyway, I guess if we ever want to enable timeout for tun, we can worry about it then. Does not need to block this patchset. > > > > -- > > MST > >