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net: sched: use queue_mapping to pick tx queue
This patch fix issue: * If we install tc filters with act_skbedit in clsact hook. It doesn't work, because netdev_core_pick_tx() overwrites queue_mapping. $ tc filter ... action skbedit queue_mapping 1 And this patch is useful: * We can use FQ + EDT to implement efficient policies. Tx queues are picked by xps, ndo_select_queue of netdev driver, or skb hash in netdev_core_pick_tx(). In fact, the netdev driver, and skb hash are _not_ under control. xps uses the CPUs map to select Tx queues, but we can't figure out which task_struct of pod/containter running on this cpu in most case. We can use clsact filters to classify one pod/container traffic to one Tx queue. Why ? In containter networking environment, there are two kinds of pod/ containter/net-namespace. One kind (e.g. P1, P2), the high throughput is key in these applications. But avoid running out of network resource, the outbound traffic of these pods is limited, using or sharing one dedicated Tx queues assigned HTB/TBF/FQ Qdisc. Other kind of pods (e.g. Pn), the low latency of data access is key. And the traffic is not limited. Pods use or share other dedicated Tx queues assigned FIFO Qdisc. This choice provides two benefits. First, contention on the HTB/FQ Qdisc lock is significantly reduced since fewer CPUs contend for the same queue. More importantly, Qdisc contention can be eliminated completely if each CPU has its own FIFO Qdisc for the second kind of pods. There must be a mechanism in place to support classifying traffic based on pods/container to different Tx queues. Note that clsact is outside of Qdisc while Qdisc can run a classifier to select a sub-queue under the lock. In general recording the decision in the skb seems a little heavy handed. This patch introduces a per-CPU variable, suggested by Eric. The skip txqueue flag will be cleared to avoid picking Tx queue in next netdev, for example (not usual case): eth0 (macvlan in Pod, skbedit queue_mapping) -> eth0.3 (vlan in Host) -> eth0 (ixgbe in Host). +----+ +----+ +----+ | P1 | | P2 | | Pn | +----+ +----+ +----+ | | | +-----------+-----------+ | | clsact/skbedit | MQ v +-----------+-----------+ | q0 | q1 | qn v v v HTB/FQ HTB/FQ ... FIFO Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Jonathan Lemon <jonathan.lemon@gmail.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Alexander Lobakin <alobakin@pm.me> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Talal Ahmad <talalahmad@google.com> Cc: Kevin Hao <haokexin@gmail.com> Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org> Cc: Kees Cook <keescook@chromium.org> Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com> Cc: Antoine Tenart <atenart@kernel.org> Cc: Wei Wang <weiwan@google.com> Cc: Arnd Bergmann <arnd@arndb.de> Suggested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
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