From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from NAM02-BL2-obe.outbound.protection.outlook.com (mail-bl2nam02on0064.outbound.protection.outlook.com [104.47.38.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xcHfK3s6SzDrCf for ; Wed, 23 Aug 2017 03:31:21 +1000 (AEST) From: Madalin Bucur To: , CC: , Subject: [PATCH v2 5/6] Documentation: networking: add RSS information Date: Tue, 22 Aug 2017 20:31:05 +0300 Message-ID: <1503423066-15420-6-git-send-email-madalin.bucur@nxp.com> In-Reply-To: <1503423066-15420-1-git-send-email-madalin.bucur@nxp.com> References: <1503423066-15420-1-git-send-email-madalin.bucur@nxp.com> Reply-To: MIME-Version: 1.0 Content-Type: text/plain List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Signed-off-by: Madalin Bucur --- Documentation/networking/dpaa.txt | 68 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 67 insertions(+), 1 deletion(-) diff --git a/Documentation/networking/dpaa.txt b/Documentation/networking/dpaa.txt index 76e016d..f88194f 100644 --- a/Documentation/networking/dpaa.txt +++ b/Documentation/networking/dpaa.txt @@ -13,6 +13,7 @@ Contents - Configuring DPAA Ethernet in your kernel - DPAA Ethernet Frame Processing - DPAA Ethernet Features + - DPAA IRQ Affinity and Receive Side Scaling - Debugging DPAA Ethernet Overview @@ -147,7 +148,10 @@ gradually. The driver has Rx and Tx checksum offloading for UDP and TCP. Currently the Rx checksum offload feature is enabled by default and cannot be controlled through -ethtool. +ethtool. Also, rx-flow-hash and rx-hashing was added. The addition of RSS +provides a big performance boost for the forwarding scenarios, allowing +different traffic flows received by one interface to be processed by different +CPUs in parallel. The driver has support for multiple prioritized Tx traffic classes. Priorities range from 0 (lowest) to 3 (highest). These are mapped to HW workqueues with @@ -166,6 +170,68 @@ classes as follows: tc qdisc add dev root handle 1: \ mqprio num_tc 4 map 0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3 hw 1 +DPAA IRQ Affinity and Receive Side Scaling +========================================== + +Traffic coming on the DPAA Rx queues or on the DPAA Tx confirmation +queues is seen by the CPU as ingress traffic on a certain portal. +The DPAA QMan portal interrupts are affined each to a certain CPU. +The same portal interrupt services all the QMan portal consumers. + +By default the DPAA Ethernet driver enables RSS, making use of the +DPAA FMan Parser and Keygen blocks to distribute traffic on 128 +hardware frame queues using a hash on IP v4/v6 source and destination +and L4 source and destination ports, in present in the received frame. +When RSS is disabled, all traffic received by a certain interface is +received on the default Rx frame queue. The default DPAA Rx frame +queues are configured to put the received traffic into a pool channel +that allows any available CPU portal to dequeue the ingress traffic. +The default frame queues have the HOLDACTIVE option set, ensuring that +traffic bursts from a certain queue are serviced by the same CPU. +This ensures a very low rate of frame reordering. A drawback of this +is that only one CPU at a time can service the traffic received by a +certain interface when RSS is not enabled. + +To implement RSS, the DPAA Ethernet driver allocates an extra set of +128 Rx frame queues that are configured to dedicated channels, in a +round-robin manner. The mapping of the frame queues to CPUs is now +hardcoded, there is no indirection table to move traffic for a certain +FQ (hash result) to another CPU. The ingress traffic arriving on one +of these frame queues will arrive at the same portal and will always +be processed by the same CPU. This ensures intra-flow order preservation +and workload distribution for multiple traffic flows. + +RSS can be turned off for a certain interface using ethtool, i.e. + + # ethtool -N fm1-mac9 rx-flow-hash tcp4 "" + +To turn it back on, one needs to set rx-flow-hash for tcp4/6 or udp4/6: + + # ethtool -N fm1-mac9 rx-flow-hash udp4 sfdn + +There is no independent control for individual protocols, any command +run for one of tcp4|udp4|ah4|esp4|sctp4|tcp6|udp6|ah6|esp6|sctp6 is +going to control the rx-flow-hashing for all protocols on that interface. + +Besides using the FMan Keygen computed hash for spreading traffic on the +128 Rx FQs, the DPAA Ethernet driver also sets the skb hash value when +the NETIF_F_RXHASH feature is on (active by default). This can be turned +on or off through ethtool, i.e.: + + # ethtool -K fm1-mac9 rx-hashing off + # ethtool -k fm1-mac9 | grep hash + receive-hashing: off + # ethtool -K fm1-mac9 rx-hashing on + Actual changes: + receive-hashing: on + # ethtool -k fm1-mac9 | grep hash + receive-hashing: on + +Please note that Rx hashing depends upon the rx-flow-hashing being on +for that interface - turning off rx-flow-hashing will also disable the +rx-hashing (without ethtool reporting it as off as that depends on the +NETIF_F_RXHASH feature flag). + Debugging ========= -- 2.1.0