Re: [v2 2/9] dpaa_eth: add support for DPAA Ethernet

Le 08/05/15 08:41, Madalin Bucur a écrit :

This introduces the Freescale Data Path Acceleration Architecture
(DPAA) Ethernet driver (dpaa_eth) that builds upon the DPAA QMan,
BMan, PAMU and FMan drivers to deliver Ethernet connectivity on
the Freescale DPAA QorIQ platforms.

Signed-off-by: Madalin Bucur <redacted>
---

[snip]

+
+if FSL_DPAA_ETH
+
+config FSL_DPAA_CS_THRESHOLD_1G
+	hex "Egress congestion threshold on 1G ports"
+	range 0x1000 0x10000000
+	default "0x06000000"

This sounds like something you would want to be able to configure at
runtime, either via private sysfs attributes, or better, using ethtool
and either a newly introduced set of tunables, or creating a private
driver API for this.

+	---help---
+	  The size in bytes of the egress Congestion State notification threshold on 1G ports.
+	  The 1G dTSECs can quite easily be flooded by cores doing Tx in a tight loop
+	  (e.g. by sending UDP datagrams at "while(1) speed"),
+	  and the larger the frame size, the more acute the problem.
+	  So we have to find a balance between these factors:
+	       - avoiding the device staying congested for a prolonged time (risking
+                 the netdev watchdog to fire - see also the tx_timeout module param);
+               - affecting performance of protocols such as TCP, which otherwise
+	         behave well under the congestion notification mechanism;
+	       - preventing the Tx cores from tightly-looping (as if the congestion
+	         threshold was too low to be effective);
+	       - running out of memory if the CS threshold is set too high.
+
+config FSL_DPAA_CS_THRESHOLD_10G
+	hex "Egress congestion threshold on 10G ports"
+	range 0x1000 0x20000000
+	default "0x10000000"
+	---help ---
+	  The size in bytes of the egress Congestion State notification threshold on 10G ports.
+
+config FSL_DPAA_INGRESS_CS_THRESHOLD
+	hex "Ingress congestion threshold on FMan ports"
+	default "0x10000000"
+	---help---
+	  The size in bytes of the ingress tail-drop threshold on FMan ports.
+	  Traffic piling up above this value will be rejected by QMan and discarded by FMan.

Same here.
-- 
Florian