netdev - [PATCH net 5/7] qeth: do not limit number of gso segments

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Date:   Thu, 15 Sep 2016 14:39:25 +0200
From:   Ursula Braun <ubraun@...ux.vnet.ibm.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        ubraun@...ux.vnet.ibm.com
Subject: [PATCH net 5/7] qeth: do not limit number of gso segments

To reduce the need of skb_linearize() calls, gso_max_segs of qeth
net_devices had been limited according to the maximum number of qdio SBAL
elements. But a gso segment cannot be larger than the mtu-size, while an
SBAL element can contain up to 4096 bytes. The gso_max_segs limitation
limits the maximum packet size given to the qeth driver. Performance
measurements with tso-enabled qeth network interfaces and mtu-size 1500
showed, that the disadvantage of smaller packets is much more severe than
the advantage of fewer skb_linearize() calls.
This patch gets rid of the gso_max_segs limitations in the qeth driver.

Signed-off-by: Ursula Braun <ubraun@...ux.vnet.ibm.com>
Reviewed-by: Thomas Richter <tmricht@...ux.vnet.ibm.com>
---
 drivers/s390/net/qeth_l2_main.c | 1 -
 drivers/s390/net/qeth_l3_main.c | 1 -
 2 files changed, 2 deletions(-)

diff --git a/drivers/s390/net/qeth_l2_main.c b/drivers/s390/net/qeth_l2_main.c
index 54fd891..2081c18 100644
--- a/drivers/s390/net/qeth_l2_main.c
+++ b/drivers/s390/net/qeth_l2_main.c
@@ -1131,7 +1131,6 @@ static int qeth_l2_setup_netdev(struct qeth_card *card)
 	qeth_l2_request_initial_mac(card);
 	card->dev->gso_max_size = (QETH_MAX_BUFFER_ELEMENTS(card) - 1) *
 				  PAGE_SIZE;
-	card->dev->gso_max_segs = (QETH_MAX_BUFFER_ELEMENTS(card) - 1);
 	SET_NETDEV_DEV(card->dev, &card->gdev->dev);
 	netif_napi_add(card->dev, &card->napi, qeth_l2_poll, QETH_NAPI_WEIGHT);
 	netif_carrier_off(card->dev);
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 4ba82e1..0cbbc80 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -3148,7 +3148,6 @@ static int qeth_l3_setup_netdev(struct qeth_card *card)
 	netif_keep_dst(card->dev);
 	card->dev->gso_max_size = (QETH_MAX_BUFFER_ELEMENTS(card) - 1) *
 				  PAGE_SIZE;
-	card->dev->gso_max_segs = (QETH_MAX_BUFFER_ELEMENTS(card) - 1);
 
 	SET_NETDEV_DEV(card->dev, &card->gdev->dev);
 	netif_napi_add(card->dev, &card->napi, qeth_l3_poll, QETH_NAPI_WEIGHT);
-- 
2.8.4