From d2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5 Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Tue, 24 Apr 2012 22:09:47 -0400 Subject: [PATCH] ppp: Don't stop and restart queue on every TX packet MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit [ 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/ppp_generic.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) 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); } -- 2.39.5