Patchwork 2.6.35-rc2, CONFIG_RPS is filling the dmesg log

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Submitter Tim Gardner
Date June 9, 2010, 1:27 p.m.
Message ID <4C0F96B4.2000307@canonical.com>
Download mbox | patch
Permalink /patch/55092/
State Superseded
Delegated to: David Miller
Headers show

Comments

Tim Gardner - June 9, 2010, 1:27 p.m.
On 06/08/2010 02:55 PM, Tim Gardner wrote:
> With 2.6.35-rc2 my dmesg log is being flooded with messages like this:
>
> br0 received packet on queue 4, but number of RX queues is 1
>
> This machine is bridged for KVM and has 2 igb network adapters.
>
> The root cause appears to be CONFIG_RPS=y and the fact that none of the
> drivers that call skb_record_rx_queue() perform their net device
> allocation using alloc_netdev_mq(), thereby initializing num_rx_queues
> to a maximum of 1.
>
> Given that this is early RPS days, is the warning in get_rps_cpu()
> really necessary? It would appear that _all_ of the multi-receive queue
> devices that call skb_record_rx_queue() will cause this log noise.
>
> By the way, how do you turn off CONFIG_RPS? The only way I could get it
> disabled was to change the default in net/Kconfig to 'n'.
>
> rtg

This is the route that I'm taking with Ubuntu in the short term. I'll 
have lots of server testers complaining pretty soon if I don't take care 
of this now. It does keep my server logs from filling.

rtg
Eric Dumazet - June 9, 2010, 1:42 p.m.
Le mercredi 09 juin 2010 à 07:27 -0600, Tim Gardner a écrit :
> On 06/08/2010 02:55 PM, Tim Gardner wrote:
> > With 2.6.35-rc2 my dmesg log is being flooded with messages like this:
> >
> > br0 received packet on queue 4, but number of RX queues is 1
> >
> > This machine is bridged for KVM and has 2 igb network adapters.
> >
> > The root cause appears to be CONFIG_RPS=y and the fact that none of the
> > drivers that call skb_record_rx_queue() perform their net device
> > allocation using alloc_netdev_mq(), thereby initializing num_rx_queues
> > to a maximum of 1.
> >
> > Given that this is early RPS days, is the warning in get_rps_cpu()
> > really necessary? It would appear that _all_ of the multi-receive queue
> > devices that call skb_record_rx_queue() will cause this log noise.
> >
> > By the way, how do you turn off CONFIG_RPS? The only way I could get it
> > disabled was to change the default in net/Kconfig to 'n'.
> >
> > rtg
> 
> This is the route that I'm taking with Ubuntu in the short term. I'll 
> have lots of server testers complaining pretty soon if I don't take care 
> of this now. It does keep my server logs from filling.
> 
> rtg
> 

Probably fine, but your commit message is not exact :

  So far no users of skb_record_rx_queue() use alloc_netdev_mq() for
  network device initialization, so don't print a warning about num_rx_queues
  imbalances in get_rps_cpu() unless they have actually been allocated.

In fact, drivers that use skb_record_rx_queue() did use alloc_netdev_mq().

Problem is : packets going thru bridge/bonding that are not yet
multiqueue enabled. If R[PF]S enabled for these "virtual devices",
we trigger the get_rps_cpu() warning.

Also, in a bonding setup, we still have a problem
because all tx packets will go thru tx queue 0 (dev_pick_tx() job)

(That might be good to know that for Ubuntu server testers)



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Patch

From 02598ea1409568654a554fae3ac2c22ecc2474d0 Mon Sep 17 00:00:00 2001
From: Tim Gardner <tim.gardner@canonical.com>
Date: Tue, 8 Jun 2010 17:51:27 -0600
Subject: [PATCH] net: Print num_rx_queues imbalance warning only when there are allocated queues

BugLink: http://bugs.launchpad.net/bugs/591416

So far no users of skb_record_rx_queue() use alloc_netdev_mq() for
network device initialization, so don't print a warning about num_rx_queues
imbalances in get_rps_cpu() unless they have actually been allocated.

Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
---
 net/core/dev.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index d03470f..0852608 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2253,7 +2253,7 @@  static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 	if (skb_rx_queue_recorded(skb)) {
 		u16 index = skb_get_rx_queue(skb);
 		if (unlikely(index >= dev->num_rx_queues)) {
-			if (net_ratelimit()) {
+			if (dev->num_rx_queues > 1 && net_ratelimit()) {
 				pr_warning("%s received packet on queue "
 					"%u, but number of RX queues is %u\n",
 					dev->name, index, dev->num_rx_queues);
-- 
1.7.0.4