The default TX queue length of Ethernet devices have been a magic constant of 1000, ever since the initial git import.
Looking back in historical trees[1][2] the value used to be 100, with the same comment "Ethernet wants good queues". The commit[3] that changed this from 100 to 1000 didn't describe why, but from conversations with Robert Olsson it seems that it was changed when Ethernet devices went from 100Mbit/s to 1Gbit/s, because the link speed increased x10 the queue size were also adjusted. This value later caused much heartache for the bufferbloat community. This patch merely moves the value into a defined constant. [1] https://git.kernel.org/cgit/linux/kernel/git/davem/netdev-vger-cvs.git/ [2] https://git.kernel.org/cgit/linux/kernel/git/tglx/history.git/ [3] https://git.kernel.org/tglx/history/c/98921832c232 Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com> --- include/net/pkt_sched.h | 2 ++ net/ethernet/eth.c | 3 ++- 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index cd334c9584e9..f1b76b8e6d2d 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -6,6 +6,8 @@ #include <linux/if_vlan.h> #include <net/sch_generic.h> +#define DEFAULT_TX_QUEUE_LEN 1000 + struct qdisc_walker { int stop; int skip; diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c index d9e2fe1da724..8c5a479681ca 100644 --- a/net/ethernet/eth.c +++ b/net/ethernet/eth.c @@ -62,6 +62,7 @@ #include <net/dsa.h> #include <net/flow_dissector.h> #include <linux/uaccess.h> +#include <net/pkt_sched.h> __setup("ether=", netdev_boot_setup); @@ -359,7 +360,7 @@ void ether_setup(struct net_device *dev) dev->min_mtu = ETH_MIN_MTU; dev->max_mtu = ETH_DATA_LEN; dev->addr_len = ETH_ALEN; - dev->tx_queue_len = 1000; /* Ethernet wants good queues */ + dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN; dev->flags = IFF_BROADCAST|IFF_MULTICAST; dev->priv_flags |= IFF_TX_SKB_SHARING;
