linux/drivers/s390
Eric Dumazet 0287587884 net: better IFF_XMIT_DST_RELEASE support
Testing xmit_more support with netperf and connected UDP sockets,
I found strange dst refcount false sharing.

Current handling of IFF_XMIT_DST_RELEASE is not optimal.

Dropping dst in validate_xmit_skb() is certainly too late in case
packet was queued by cpu X but dequeued by cpu Y

The logical point to take care of drop/force is in __dev_queue_xmit()
before even taking qdisc lock.

As Julian Anastasov pointed out, need for skb_dst() might come from some
packet schedulers or classifiers.

This patch adds new helper to cleanly express needs of various drivers
or qdiscs/classifiers.

Drivers that need skb_dst() in their ndo_start_xmit() should call
following helper in their setup instead of the prior :

	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
->
	netif_keep_dst(dev);

Instead of using a single bit, we use two bits, one being
eventually rebuilt in bonding/team drivers.

The other one, is permanent and blocks IFF_XMIT_DST_RELEASE being
rebuilt in bonding/team. Eventually, we could add something
smarter later.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-10-07 13:22:11 -04:00
..
block s390/dasd: Make module parameter visible in sysfs 2014-09-01 09:56:28 +02:00
char s390/sclp: remove unnecessary XTABS flag 2014-08-15 09:01:20 +02:00
cio s390/qdio: add helpers to manage qdio buffers 2014-07-22 09:26:13 +02:00
crypto s390/zcrypt: improve device probing for zcrypt adapter cards 2014-07-16 10:48:12 +02:00
kvm virtio_ccw: introduce device_lost in virtio_ccw_device 2014-04-28 11:34:13 +09:30
net net: better IFF_XMIT_DST_RELEASE support 2014-10-07 13:22:11 -04:00
scsi Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-08-07 08:41:00 -07:00
Makefile