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| author | David Woodhouse <David.Woodhouse@intel.com> | 2012-04-24 22:09:47 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-04-27 09:51:18 -0700 |
| commit | d2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5 (patch) | |
| tree | a6d2e7f3e0c3f489ca960b46b2b40a1d97a6b4be | |
| parent | 9740f1d824f30d9961ab406990e3a420299afb6f (diff) | |
| download | linux-stable-d2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5.tar.gz linux-stable-d2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5.tar.bz2 linux-stable-d2491ed1e1c5bf2db6ab44eb5bfe38b48043b2d5.zip | |
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.c | 3 |
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); } |