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authorDavid Woodhouse <David.Woodhouse@intel.com>2012-04-24 22:09:47 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-04-27 09:51:18 -0700
commitd2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5 (patch)
treea6d2e7f3e0c3f489ca960b46b2b40a1d97a6b4be
parent9740f1d824f30d9961ab406990e3a420299afb6f (diff)
ppp: Don't stop and restart queue on every TX packet
[ This combines upstream commit e675f0cc9a872fd152edc0c77acfed19bf28b81e and follow-on bug fix commit 9a5d2bd99e0dfe9a31b3c160073ac445ba3d773f ] For every transmitted packet, ppp_start_xmit() will stop the netdev queue and then, if appropriate, restart it. This causes the TX softirq to run, entirely gratuitously. This is "only" a waste of CPU time in the normal case, but it's actively harmful when the PPP device is a TEQL slave — the wakeup will cause the offending device to receive the next TX packet from the TEQL queue, when it *should* have gone to the next slave in the list. We end up seeing large bursts of packets on just *one* slave device, rather than using the full available bandwidth over all slaves. This patch fixes the problem by *not* unconditionally stopping the queue in ppp_start_xmit(). It adds a return value from ppp_xmit_process() which indicates whether the queue should be stopped or not. It *doesn't* remove the call to netif_wake_queue() from ppp_xmit_process(), because other code paths (especially from ppp_output_wakeup()) need it there and it's messy to push it out to the other callers to do it based on the return value. So we leave it in place — it's a no-op in the case where the queue wasn't stopped, so it's harmless in the TX path. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/net/ppp_generic.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 33d013139217..b890401cab93 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -968,7 +968,6 @@ ppp_start_xmit(struct sk_buff *skb, struct net_device *dev)
proto = npindex_to_proto[npi];
put_unaligned_be16(proto, pp);
- netif_stop_queue(dev);
skb_queue_tail(&ppp->file.xq, skb);
ppp_xmit_process(ppp);
return NETDEV_TX_OK;
@@ -1063,6 +1062,8 @@ ppp_xmit_process(struct ppp *ppp)
code that we can accept some more. */
if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq))
netif_wake_queue(ppp->dev);
+ else
+ netif_stop_queue(ppp->dev);
}
ppp_xmit_unlock(ppp);
}