X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=15net%2Fnet;h=491e84b0f313e831a135d9a234dea4b4694cf139;hb=f4619770cba88e3f6451fba46016f91ef666f4a9;hp=4e0b7e7702e2a3f7c1a7e02f4fcb27bcac30dfcc;hpb=8a090421baae2f8d105e6338c8f8f4b11e8a2346;p=cascardo%2Fkernel%2Fslides%2F.git

diff --git a/15net/net b/15net/net
index 4e0b7e7..491e84b 100644
--- a/15net/net
+++ b/15net/net
@@ -91,8 +91,53 @@
 * Current code already updates last time packet was transmitted
 * Driver should set watchdog\\_timeo and ndo\\_tx\\_timeout
 
+# Reception
+
+* Usually happens in an interrupt handler
+* Driver allocates skb: some drivers allocate it when setting up and arrange the
+  device to write into the buffers directly
+* Must set skb field protocol: easily done for ethernet drivers with
+  eth\\_type\\_trans
+* Finally, call netif\\_rx
+
+# NAPI
+
+* To allow more performance, NAPI introduces polling, avoiding too much
+  interrupts when load is high
+* Driver disables interrupts and enables polling in its interrupt handler
+  when RX happens
+* Network subsystem uses a softirq to do the polling
+* The driver poll function disables polling and reenabled interrupts when it's
+  done with its hardware queue
+
 # NAPI
 
+* struct napi\\_struct
+* netif\\_napi\\_add(dev, napi, poll\\_func, weight)
+* napi\\_enable: called in open
+* napi\\_disable: called in stop - awaits completion
+* napi\\_schedule
+	- napi\\_schedule\\_prep
+	- \\_\\_napi\\_schedule
+* napi\\_complete: called in poll when all is done
+* Use netif\\_receive\\_skb instead of netif\\_rx
+
+# NAPI step by step
+
+* In the interrupt handler:
+	- Checks that the interrupt received is RX
+	- Call napi\\_schedule\\_prep to check that napi isn't already scheduled
+	- Disable RX
+	- Call \\_\\_napi\\_schedule
+
+# Weight and Budget
+
+* The weight is the start budget for the interface, usually 16
+* The poll function must not dequeue more frames than the budget
+* It must call napi\\_complete if and only if it has exhausted the hardware
+  queues with less than the budget
+* It must return the number of entries in the queue processed
+
 # Changes in net device
 
 * Use netdev\\_priv, no priv anymore
@@ -104,6 +149,10 @@
 # Other recent changes
 
 * Some members moved to netdev\\_queue to increase cache-line usage
-* GRO/GSO
-* Multi-queue support
-* RPS - Packet Steering
+* GRO/GSO - Handle hardware checksum acceleration
+* Multi-queue support, for devices with multiple queues, so they can be handled
+  in different CPUs
+* RPS - Receive Packet Steering, which distributes protocol processing amongst
+  multiple CPUs in case of a single device, single queue system
+* RFS - Receive Flow Steering, which tries to handle the packet in the CPU where
+  the application is running