linux_dsm_epyc7002/drivers/s390
Julian Wiedmann 0d6f02d375 s390/qeth: use skb_cow_head() for L2 OSA xmit
Taking a full copy via skb_realloc_headroom() on every xmit is overkill
and wastes CPU time; all we actually need is to push on the qeth_hdr.
So rework the L2 OSA TX path to avoid the copy.
Minor complications arise because struct qeth_hdr must not cross a page
boundary. So add a new helper qeth_push_hdr() that catches this, and
falls back to the hdr cache that we already use for IQDs.

This change uncovered that qeth's TX completion takes rather long.
Now that we no longer free the original skb straight away and thus call
skb->destructor later than before, throughput regresses significantly.
For now, restore old behaviour by adding an explicit skb_orphan(),
and a big TODO to improve the TX completion time.

Tested-by: Nils Hoppmann <niho@de.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-08-18 10:21:30 -07:00
..
block libnvdimm for 4.13 2017-07-07 09:44:06 -07:00
char mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful semantic 2017-07-12 16:26:03 -07:00
cio s390: chp: handle CRW_ERC_INIT for channel-path status change 2017-07-13 11:28:29 +02:00
crypto s390/zcrypt: Fix missing newlines at some debug feature messages. 2017-07-05 07:35:29 +02:00
net s390/qeth: use skb_cow_head() for L2 OSA xmit 2017-08-18 10:21:30 -07:00
scsi SCSI misc on 20170220 2017-02-21 11:51:42 -08:00
virtio Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2017-05-16 09:24:44 -07:00
Makefile virtio/s390: rename drivers/s390/kvm -> drivers/s390/virtio 2015-07-07 14:27:06 +03:00