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| author | David Woodhouse <dwmw2@infradead.org> | 2012-03-26 00:03:42 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-04-03 17:31:38 -0400 |
| commit | e675f0cc9a872fd152edc0c77acfed19bf28b81e (patch) | |
| tree | 244c4488575cc19bd882ad00c2d6852db5bcbe98 /drivers/net | |
| parent | 2def16ae6b0c77571200f18ba4be049b03d75579 (diff) | |
| download | blackbird-op-linux-e675f0cc9a872fd152edc0c77acfed19bf28b81e.tar.gz blackbird-op-linux-e675f0cc9a872fd152edc0c77acfed19bf28b81e.zip | |
ppp: Don't stop and restart queue on every TX packet
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>
Diffstat (limited to 'drivers/net')
| -rw-r--r-- | drivers/net/ppp/ppp_generic.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 159da2905fe9..33f8c51968b6 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -235,7 +235,7 @@ struct ppp_net { /* Prototypes. */ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf, struct file *file, unsigned int cmd, unsigned long arg); -static void ppp_xmit_process(struct ppp *ppp); +static int ppp_xmit_process(struct ppp *ppp); static void ppp_send_frame(struct ppp *ppp, struct sk_buff *skb); static void ppp_push(struct ppp *ppp); static void ppp_channel_push(struct channel *pch); @@ -968,9 +968,9 @@ 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); + if (!ppp_xmit_process(ppp)) + netif_stop_queue(dev); return NETDEV_TX_OK; outf: @@ -1048,10 +1048,11 @@ static void ppp_setup(struct net_device *dev) * Called to do any work queued up on the transmit side * that can now be done. */ -static void +static int ppp_xmit_process(struct ppp *ppp) { struct sk_buff *skb; + int ret = 0; ppp_xmit_lock(ppp); if (!ppp->closing) { @@ -1061,10 +1062,13 @@ ppp_xmit_process(struct ppp *ppp) ppp_send_frame(ppp, skb); /* If there's no work left to do, tell the core net code that we can accept some more. */ - if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) + if (!ppp->xmit_pending && !skb_peek(&ppp->file.xq)) { netif_wake_queue(ppp->dev); + ret = 1; + } } ppp_xmit_unlock(ppp); + return ret; } static inline struct sk_buff * |
