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91 files changed, 1758 insertions, 2375 deletions
diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl index b886f52a9aa..e5da4f2b7c2 100644 --- a/Documentation/DocBook/kernel-api.tmpl +++ b/Documentation/DocBook/kernel-api.tmpl @@ -240,17 +240,23 @@ X!Ilib/string.c <sect1><title>Driver Support</title> !Enet/core/dev.c !Enet/ethernet/eth.c +!Enet/sched/sch_generic.c !Iinclude/linux/etherdevice.h +!Iinclude/linux/netdevice.h + </sect1> + <sect1><title>PHY Support</title> !Edrivers/net/phy/phy.c !Idrivers/net/phy/phy.c !Edrivers/net/phy/phy_device.c !Idrivers/net/phy/phy_device.c !Edrivers/net/phy/mdio_bus.c !Idrivers/net/phy/mdio_bus.c + </sect1> <!-- FIXME: Removed for now since no structured comments in source + <sect1><title>Wireless</title> X!Enet/core/wireless.c ---> </sect1> +--> <sect1><title>Synchronous PPP</title> !Edrivers/net/wan/syncppp.c </sect1> diff --git a/Documentation/networking/NAPI_HOWTO.txt b/Documentation/networking/NAPI_HOWTO.txt deleted file mode 100644 index 7907435a661..00000000000 --- a/Documentation/networking/NAPI_HOWTO.txt +++ /dev/null @@ -1,766 +0,0 @@ -HISTORY: -February 16/2002 -- revision 0.2.1: -COR typo corrected -February 10/2002 -- revision 0.2: -some spell checking ;-> -January 12/2002 -- revision 0.1 -This is still work in progress so may change. -To keep up to date please watch this space. - -Introduction to NAPI -==================== - -NAPI is a proven (www.cyberus.ca/~hadi/usenix-paper.tgz) technique -to improve network performance on Linux. For more details please -read that paper. -NAPI provides a "inherent mitigation" which is bound by system capacity -as can be seen from the following data collected by Robert on Gigabit -ethernet (e1000): - - Psize Ipps Tput Rxint Txint Done Ndone - --------------------------------------------------------------- - 60 890000 409362 17 27622 7 6823 - 128 758150 464364 21 9301 10 7738 - 256 445632 774646 42 15507 21 12906 - 512 232666 994445 241292 19147 241192 1062 - 1024 119061 1000003 872519 19258 872511 0 - 1440 85193 1000003 946576 19505 946569 0 - - -Legend: -"Ipps" stands for input packets per second. -"Tput" == packets out of total 1M that made it out. -"txint" == transmit completion interrupts seen -"Done" == The number of times that the poll() managed to pull all -packets out of the rx ring. Note from this that the lower the -load the more we could clean up the rxring -"Ndone" == is the converse of "Done". Note again, that the higher -the load the more times we couldn't clean up the rxring. - -Observe that: -when the NIC receives 890Kpackets/sec only 17 rx interrupts are generated. -The system cant handle the processing at 1 interrupt/packet at that load level. -At lower rates on the other hand, rx interrupts go up and therefore the -interrupt/packet ratio goes up (as observable from that table). So there is -possibility that under low enough input, you get one poll call for each -input packet caused by a single interrupt each time. And if the system -cant handle interrupt per packet ratio of 1, then it will just have to -chug along .... - - -0) Prerequisites: -================== -A driver MAY continue using the old 2.4 technique for interfacing -to the network stack and not benefit from the NAPI changes. -NAPI additions to the kernel do not break backward compatibility. -NAPI, however, requires the following features to be available: - -A) DMA ring or enough RAM to store packets in software devices. - -B) Ability to turn off interrupts or maybe events that send packets up -the stack. - -NAPI processes packet events in what is known as dev->poll() method. -Typically, only packet receive events are processed in dev->poll(). -The rest of the events MAY be processed by the regular interrupt handler -to reduce processing latency (justified also because there are not that -many of them). -Note, however, NAPI does not enforce that dev->poll() only processes -receive events. -Tests with the tulip driver indicated slightly increased latency if -all of the interrupt handler is moved to dev->poll(). Also MII handling -gets a little trickier. -The example used in this document is to move the receive processing only -to dev->poll(); this is shown with the patch for the tulip driver. -For an example of code that moves all the interrupt driver to -dev->poll() look at the ported e1000 code. - -There are caveats that might force you to go with moving everything to -dev->poll(). Different NICs work differently depending on their status/event -acknowledgement setup. -There are two types of event register ACK mechanisms. - I) what is known as Clear-on-read (COR). - when you read the status/event register, it clears everything! - The natsemi and sunbmac NICs are known to do this. - In this case your only choice is to move all to dev->poll() - - II) Clear-on-write (COW) - i) you clear the status by writing a 1 in the bit-location you want. - These are the majority of the NICs and work the best with NAPI. - Put only receive events in dev->poll(); leave the rest in - the old interrupt handler. - ii) whatever you write in the status register clears every thing ;-> - Cant seem to find any supported by Linux which do this. If - someone knows such a chip email us please. - Move all to dev->poll() - -C) Ability to detect new work correctly. -NAPI works by shutting down event interrupts when there's work and -turning them on when there's none. -New packets might show up in the small window while interrupts were being -re-enabled (refer to appendix 2). A packet might sneak in during the period -we are enabling interrupts. We only get to know about such a packet when the -next new packet arrives and generates an interrupt. -Essentially, there is a small window of opportunity for a race condition -which for clarity we'll refer to as the "rotting packet". - -This is a very important topic and appendix 2 is dedicated for more -discussion. - -Locking rules and environmental guarantees -========================================== - --Guarantee: Only one CPU at any time can call dev->poll(); this is because -only one CPU can pick the initial interrupt and hence the initial -netif_rx_schedule(dev); -- The core layer invokes devices to send packets in a round robin format. -This implies receive is totally lockless because of the guarantee that only -one CPU is executing it. -- contention can only be the result of some other CPU accessing the rx -ring. This happens only in close() and suspend() (when these methods -try to clean the rx ring); -****guarantee: driver authors need not worry about this; synchronization -is taken care for them by the top net layer. --local interrupts are enabled (if you dont move all to dev->poll()). For -example link/MII and txcomplete continue functioning just same old way. -This improves the latency of processing these events. It is also assumed that -the receive interrupt is the largest cause of noise. Note this might not -always be true. -[according to Manfred Spraul, the winbond insists on sending one -txmitcomplete interrupt for each packet (although this can be mitigated)]. -For these broken drivers, move all to dev->poll(). - -For the rest of this text, we'll assume that dev->poll() only -processes receive events. - -new methods introduce by NAPI -============================= - -a) netif_rx_schedule(dev) -Called by an IRQ handler to schedule a poll for device - -b) netif_rx_schedule_prep(dev) -puts the device in a state which allows for it to be added to the -CPU polling list if it is up and running. You can look at this as -the first half of netif_rx_schedule(dev) above; the second half -being c) below. - -c) __netif_rx_schedule(dev) -Add device to the poll list for this CPU; assuming that _prep above -has already been called and returned 1. - -d) netif_rx_reschedule(dev, undo) -Called to reschedule polling for device specifically for some -deficient hardware. Read Appendix 2 for more details. - -e) netif_rx_complete(dev) - -Remove interface from the CPU poll list: it must be in the poll list -on current cpu. This primitive is called by dev->poll(), when -it completes its work. The device cannot be out of poll list at this -call, if it is then clearly it is a BUG(). You'll know ;-> - -All of the above methods are used below, so keep reading for clarity. - -Device driver changes to be made when porting NAPI -================================================== - -Below we describe what kind of changes are required for NAPI to work. - -1) introduction of dev->poll() method -===================================== - -This is the method that is invoked by the network core when it requests -for new packets from the driver. A driver is allowed to send upto -dev->quota packets by the current CPU before yielding to the network -subsystem (so other devices can also get opportunity to send to the stack). - -dev->poll() prototype looks as follows: -int my_poll(struct net_device *dev, int *budget) - -budget is the remaining number of packets the network subsystem on the -current CPU can send up the stack before yielding to other system tasks. -*Each driver is responsible for decrementing budget by the total number of -packets sent. - Total number of packets cannot exceed dev->quota. - -dev->poll() method is invoked by the top layer, the driver just sends if it -can to the stack the packet quantity requested. - -more on dev->poll() below after the interrupt changes are explained. - -2) registering dev->poll() method -=================================== - -dev->poll should be set in the dev->probe() method. -e.g: -dev->open = my_open; -. -. -/* two new additions */ -/* first register my poll method */ -dev->poll = my_poll; -/* next register my weight/quanta; can be overridden in /proc */ -dev->weight = 16; -. -. -dev->stop = my_close; - - - -3) scheduling dev->poll() -============================= -This involves modifying the interrupt handler and the code -path which takes the packet off the NIC and sends them to the -stack. - -it's important at this point to introduce the classical D Becker -interrupt processor: - ------------------- -static irqreturn_t -netdevice_interrupt(int irq, void *dev_id, struct pt_regs *regs) -{ - - struct net_device *dev = (struct net_device *)dev_instance; - struct my_private *tp = (struct my_private *)dev->priv; - - int work_count = my_work_count; - status = read_interrupt_status_reg(); - if (status == 0) - return IRQ_NONE; /* Shared IRQ: not us */ - if (status == 0xffff) - return IRQ_HANDLED; /* Hot unplug */ - if (status & error) - do_some_error_handling() - - do { - acknowledge_ints_ASAP(); - - if (status & link_interrupt) { - spin_lock(&tp->link_lock); - do_some_link_stat_stuff(); - spin_lock(&tp->link_lock); - } - - if (status & rx_interrupt) { - receive_packets(dev); - } - - if (status & rx_nobufs) { - make_rx_buffs_avail(); - } - - if (status & tx_related) { - spin_lock(&tp->lock); - tx_ring_free(dev); - if (tx_died) - restart_tx(); |