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Add RX quotas to the net device poll() method. This avoids the problem

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of alloc_pkb() exhaustion when e.g. an iSCSI-booted DOS session is left
idle for a long time at the C:\ prompt and builds up a huge packet
backlog.
This commit is contained in:
Michael Brown
2007-01-09 21:47:01 +00:00
parent e822bc2a90
commit c65fae2475
6 changed files with 75 additions and 36 deletions
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38
src/net/netdevice.c
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@@ -126,16 +126,17 @@ void netdev_rx ( struct net_device *netdev, struct pk_buff *pkb ) {
* Poll for packet on network device
*
* @v netdev Network device
* @v rx_quota Maximum number of packets to receive
* @ret True There are packets present in the receive queue
* @ret False There are no packets present in the receive queue
*
* Polls the network device for received packets. Any received
* packets will be added to the RX packet queue via netdev_rx().
*/
int netdev_poll ( struct net_device *netdev ) {
int netdev_poll ( struct net_device *netdev, unsigned int rx_quota ) {
if ( netdev->state & NETDEV_OPEN )
netdev->poll ( netdev );
netdev->poll ( netdev, rx_quota );
return ( ! list_empty ( &netdev->rx_queue ) );
}
@@ -351,14 +352,9 @@ int net_rx ( struct pk_buff *pkb, struct net_device *netdev,
*
* @v process Network stack process
*
* This polls all interfaces for any received packets, and processes
* at most one packet from the RX queue.
* This polls all interfaces for received packets, and processes
* packets from the RX queue.
*
* We avoid processing all received packets, because processing the
* received packet can trigger transmission of a new packet (e.g. an
* ARP response). Since TX completions will be processed as part of
* the poll operation, it is easy to overflow small TX queues if
* multiple packets are processed per poll.
*/
static void net_step ( struct process *process ) {
struct net_device *netdev;
@@ -367,10 +363,28 @@ static void net_step ( struct process *process ) {
/* Poll and process each network device */
list_for_each_entry ( netdev, &net_devices, list ) {
/* Poll for new packets */
netdev_poll ( netdev );
/* Poll for new packets. Limit RX queue size to a
* single packet, because otherwise most drivers are
* in serious danger of running out of memory and
* having to drop packets.
*
* This limitation isn't relevant to devices that
* preallocate packet buffers (i.e. devices with
* descriptor-based RX datapaths). We might at some
* point want to relax the quota for such devices.
*/
netdev_poll ( netdev,
( list_empty ( &netdev->rx_queue ) ? 1 : 0 ) );
/* Handle at most one received packet per poll */
/* Handle at most one received packet per poll. We
* avoid processing more than one packet per call to
* netdev_poll(), because processing the received
* packet can trigger transmission of a new packet
* (e.g. an ARP response). Since TX completions will
* be processed as part of the poll operation, it is
* easy to overflow small TX queues if multiple
* packets are processed per poll.
*/
if ( ( pkb = netdev_rx_dequeue ( netdev ) ) ) {
DBGC ( netdev, "NETDEV %p processing %p\n",
netdev, pkb );