group.of.nepali.translators team mailing list archive

[Kleber Sacilotto de Souza <kleber.souza@xxxxxxxxxxxxx>]

** Also affects: linux-gcp (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Also affects: linux-gke-5.0 (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux-gcp (Ubuntu Xenial)
       Status: New => In Progress

** Changed in: linux-gke-5.0 (Ubuntu Xenial)
       Status: New => Invalid

** Changed in: linux-gcp (Ubuntu Xenial)
       Status: In Progress => Fix Committed

** Also affects: linux-gke-4.15 (Ubuntu)
   Importance: Undecided
       Status: New

** Changed in: linux-gke-4.15 (Ubuntu Bionic)
       Status: New => Fix Committed

** Changed in: linux-gke-4.15 (Ubuntu Xenial)
       Status: New => Invalid

** Changed in: linux-gke-4.15 (Ubuntu Disco)
       Status: New => Invalid

** Changed in: linux-gke-4.15 (Ubuntu)
       Status: New => Invalid

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https://bugs.launchpad.net/bugs/1834681

Title:
  Enable napi_tx for GCP/GKE kernels

Status in linux-gcp package in Ubuntu:
  Invalid
Status in linux-gke-4.15 package in Ubuntu:
  Invalid
Status in linux-gke-5.0 package in Ubuntu:
  Invalid
Status in linux-gcp source package in Xenial:
  Fix Committed
Status in linux-gke-4.15 source package in Xenial:
  Invalid
Status in linux-gke-5.0 source package in Xenial:
  Invalid
Status in linux-gcp source package in Bionic:
  Invalid
Status in linux-gke-4.15 source package in Bionic:
  Fix Committed
Status in linux-gke-5.0 source package in Bionic:
  In Progress
Status in linux-gcp source package in Disco:
  In Progress
Status in linux-gke-4.15 source package in Disco:
  Invalid
Status in linux-gke-5.0 source package in Disco:
  Invalid

Bug description:
  Background: Napi_tx is a Linux kernel feature that makes the virtio
  driver call the skb destructor after the packets are actually “out”
  (i.e., at TX completion interrupt), as opposed to immediately after
  the packets are enqueued. This provides socket backpressure and is
  critical for features such as TSQ. Enabling napi_tx in Cloud guests is
  an indispensable link in the chain of end-to-end backpressure from
  USPS all the way up to the guest applications. It would help reduce
  bufferbloat, packet drops and/or avoid HoL blocking when the traffic
  from the VMs are rate limited (due to congestion/BwE/etc).

  The GCP networking engineering teams have asked us to include and
  enable napi_tx on the major guest OS's on the platform. They have 6
  months of performance and regression testing and are comfortable
  moving forward with this broadly.

  The main request is to change this module parameter: 
  +++ b/drivers/net/virtio_net.c 
  @@ -26,7 +26,7 @@ 
  static int napi_weight = NAPI_POLL_WEIGHT; 
  module_param(napi_weight, int, 0444); 

  -static bool csum = true, gso = true, napi_tx; 
  +static bool csum = true, gso = true, napi_tx = true; 

  That is either the above kernel change or a configuration change at
  module load. Note that that also gives us a simple resolution in the
  unlikely case that this causes a regression on some workloads.

  Besides the main switch, kernels need these other prerequisite
  patches:

  The main feature, in 4.12-rc1:

  1d11e732e7d50 virtio-net: use netif_tx_napi_add for tx napi 
  78a57b482aa53 virtio-net: on tx, only call napi_disable if tx napi is on 
  bdb12e0d2ffc8 virtio-net: keep tx interrupts disabled unless kick 
  7b0411ef4aa69 virtio-net: clean tx descriptors from rx napi 
  ea7735d97ba90 virtio-net: move free_old_xmit_skbs 
  b92f1e6751a6a virtio-net: transmit napi 
  e4e8452a4ab30 virtio-net: napi helper functions 

  Virtio-net queue affinity, in 4.19-rc1:

  2ca653d607ce5 virtio_net: Stripe queue affinities across cores. 
  19e226e8cc5da virtio: Make vp_set_vq_affinity() take a mask. 
  9af18e56d43ca cpumask: make cpumask_next_wrap available without smp 

  A nice to have is ethtool support to test whether the feature is
  enabled, in 5.1-rc1:

  133bbb18ab1a2 virtio-net: per-queue RPS config

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