netdev - [PATCH] sis900: re-enable high throughput

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Message-Id: <20190607172628.31471-1-sergej.benilov@googlemail.com>
Date:   Fri,  7 Jun 2019 19:26:28 +0200
From:   Sergej Benilov <sergej.benilov@...glemail.com>
To:     venza@...wnhat.org, netdev@...r.kernel.org
Cc:     Sergej Benilov <sergej.benilov@...glemail.com>
Subject: [PATCH] sis900: re-enable high throughput

Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing",
the TSQ limit is computed as the smaller of
sysctl_tcp_limit_output_bytes and max(2 * skb->truesize, sk->sk_pacing_rate >> 10).
For some connections this approach sets a low limit, reducing throughput dramatically.

Add a call to skb_orphan() to sis900_start_xmit()
to speed up packets delivery from the kernel to the driver.

Test:
netperf -H remote -l -2000000 -- -s 1000000

before patch:

MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380 327680 327680    341.79      0.05

after patch:

MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to remote () port 0 AF_INET : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380 327680 327680    1.29       12.54

Signed-off-by: Sergej Benilov <sergej.benilov@...glemail.com>
---
 drivers/net/ethernet/sis/sis900.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/sis/sis900.c b/drivers/net/ethernet/sis/sis900.c
index fd812d2e..ca17b50c 100644
--- a/drivers/net/ethernet/sis/sis900.c
+++ b/drivers/net/ethernet/sis/sis900.c
@@ -1604,6 +1604,7 @@ sis900_start_xmit(struct sk_buff *skb, struct net_device *net_dev)
 	unsigned int  index_cur_tx, index_dirty_tx;
 	unsigned int  count_dirty_tx;

+	skb_orphan(skb);
 	spin_lock_irqsave(&sis_priv->lock, flags);

 	/* Calculate the next Tx descriptor entry. */
-- 
2.17.1