|
|
@@ -0,0 +1,82 @@
|
|
|
+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 <[email protected]>
|
|
|
+
|
|
|
+--- a/drivers/net/ppp/ppp_generic.c~ 2012-01-26 00:39:32.000000000 +0000
|
|
|
++++ b/drivers/net/ppp/ppp_generic.c 2012-03-26 10:32:31.286744147 +0100
|
|
|
+@@ -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, stru
|
|
|
+ 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
|
|
|
+ * 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 *
|
|
|
+
|
|
|
+--
|
|
|
+David Woodhouse Open Source Technology Centre
|
|
|
[email protected] Intel Corporation
|
|
|
+
|
|
|
+
|
|
|
+
|
Florian Fainelli