diff options
Diffstat (limited to 'target/linux/generic/patches-3.2/120-ppp_txqueue_restart.patch')
| -rw-r--r-- | target/linux/generic/patches-3.2/120-ppp_txqueue_restart.patch | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/target/linux/generic/patches-3.2/120-ppp_txqueue_restart.patch b/target/linux/generic/patches-3.2/120-ppp_txqueue_restart.patch new file mode 100644 index 0000000000..83033a16c2 --- /dev/null +++ b/target/linux/generic/patches-3.2/120-ppp_txqueue_restart.patch @@ -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 <David.Woodhouse@intel.com> + +--- 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 +David.Woodhouse@intel.com Intel Corporation + + + |