diff options
| author |   Julian Wiedmann <jwi@linux.vnet.ibm.com> | 2017-12-01 10:14:50 +0100 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2017-12-02 21:35:21 -0500 |
| commit | 6d69b1f1eb7a2edf8a3547f361c61f2538e054bb (patch) | |
| tree | 11944d807ae8a95faa6a3f77491a52cbe0bd1378 /drivers/s390/net/qeth_core.h | |
| parent | s390/qeth: fix thinko in IPv4 multicast address tracking (diff) | |
| download | linux-dev-6d69b1f1eb7a2edf8a3547f361c61f2538e054bb.tar.xz linux-dev-6d69b1f1eb7a2edf8a3547f361c61f2538e054bb.zip | |
s390/qeth: fix GSO throughput regression
Using GSO with small MTUs currently results in a substantial throughput
regression - which is caused by how qeth needs to map non-linear skbs
into its IO buffer elements:
compared to a linear skb, each GSO-segmented skb effectively consumes
twice as many buffer elements (ie two instead of one) due to the
additional header-only part. This causes the Output Queue to be
congested with low-utilized IO buffers.
Fix this as follows:
If the MSS is low enough so that a non-SG GSO segmentation produces
order-0 skbs (currently ~3500 byte), opt out from NETIF_F_SG. This is
where we anticipate the biggest savings, since an SG-enabled
GSO segmentation produces skbs that always consume at least two
buffer elements.
Larger MSS values continue to get a SG-enabled GSO segmentation, since
1) the relative overhead of the additional header-only buffer element
becomes less noticeable, and
2) the linearization overhead increases.
With the throughput regression fixed, re-enable NETIF_F_SG by default to
reap the significant CPU savings of GSO.
Fixes: 5722963a8e83 ("qeth: do not turn on SG per default")
Reported-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>
Diffstat (limited to 'drivers/s390/net/qeth_core.h')
| -rw-r--r-- | drivers/s390/net/qeth_core.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h index 9cd569ef43ec..15015a24f8ad 100644 --- a/drivers/s390/net/qeth_core.h +++ b/drivers/s390/net/qeth_core.h @@ -987,6 +987,9 @@ struct qeth_cmd_buffer *qeth_get_setassparms_cmd(struct qeth_card *, int qeth_set_features(struct net_device *, netdev_features_t); void qeth_recover_features(struct net_device *dev); netdev_features_t qeth_fix_features(struct net_device *, netdev_features_t); +netdev_features_t qeth_features_check(struct sk_buff *skb, + struct net_device *dev, + netdev_features_t features); int qeth_vm_request_mac(struct qeth_card *card); int qeth_push_hdr(struct sk_buff *skb, struct qeth_hdr **hdr, unsigned int len); |