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Date: Sat, 19 Feb 2011 21:27:37 +0100
From: Nicolas de Pesloüan
<nicolas.2p.debian@...il.com>
To: Jiri Pirko <jpirko@...hat.com>
CC: Jay Vosburgh <fubar@...ibm.com>,
David Miller <davem@...emloft.net>, kaber@...sh.net,
eric.dumazet@...il.com, netdev@...r.kernel.org,
shemminger@...ux-foundation.org, andy@...yhouse.net
Subject: Re: [patch net-next-2.6 V3] net: convert bonding to use rx_handler
Le 19/02/2011 14:46, Jiri Pirko a écrit :
> Sat, Feb 19, 2011 at 02:18:00PM CET, nicolas.2p.debian@...il.com wrote:
>> Le 19/02/2011 12:28, Jiri Pirko a écrit :
>>> Sat, Feb 19, 2011 at 12:08:31PM CET, jpirko@...hat.com wrote:
>>>> Sat, Feb 19, 2011 at 11:56:23AM CET, nicolas.2p.debian@...il.com wrote:
>>>>> Le 19/02/2011 09:05, Jiri Pirko a écrit :
>>>>>> This patch converts bonding to use rx_handler. Results in cleaner
>>>>>> __netif_receive_skb() with much less exceptions needed. Also
>>>>>> bond-specific work is moved into bond code.
>>>>>>
>>>>>> Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>>>>>
>>>>>> v1->v2:
>>>>>> using skb_iif instead of new input_dev to remember original
>>>>>> device
>>>>>> v2->v3:
>>>>>> set orig_dev = skb->dev if skb_iif is set
>>>>>>
>>>>>
>>>>> Why do we need to let the rx_handlers call netif_rx() or __netif_receive_skb()?
>>>>>
>>>>> Bonding used to be handled with very few overhead, simply replacing
>>>>> skb->dev with skb->dev->master. Time has passed and we eventually
>>>>> added many special processing for bonding into __netif_receive_skb(),
>>>>> but the overhead remained very light.
>>>>>
>>>>> Calling netif_rx() (or __netif_receive_skb()) to allow nesting would probably lead to some overhead.
>>>>>
>>>>> Can't we, instead, loop inside __netif_receive_skb(), and deliver
>>>>> whatever need to be delivered, to whoever need, inside the loop ?
>>>>>
>>>>> rx_handler = rcu_dereference(skb->dev->rx_handler);
>>>>> while (rx_handler) {
>>>>> /* ... */
>>>>> orig_dev = skb->dev;
>>>>> skb = rx_handler(skb);
>>>>> /* ... */
>>>>> rx_handler = (skb->dev != orig_dev) ? rcu_dereference(skb->dev->rx_handler) : NULL;
>>>>> }
>>>>>
>>>>> This would reduce the overhead, while still allowing nesting: vlan on
>>>>> top on bonding, bridge on top on bonding, ...
>>>>
>>>> I see your point. Makes sense to me. But the loop would have to include
>>>> at least processing of ptype_all too. I'm going to cook a follow-up
>>>> patch.
>>>>
>>>
>>> DRAFT (doesn't modify rx_handlers):
>>>
>>> diff --git a/net/core/dev.c b/net/core/dev.c
>>> index 4ebf7fe..e5dba47 100644
>>> --- a/net/core/dev.c
>>> +++ b/net/core/dev.c
>>> @@ -3115,6 +3115,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
>>> {
>>> struct packet_type *ptype, *pt_prev;
>>> rx_handler_func_t *rx_handler;
>>> + struct net_device *dev;
>>> struct net_device *orig_dev;
>>> struct net_device *null_or_dev;
>>> int ret = NET_RX_DROP;
>>> @@ -3129,7 +3130,9 @@ static int __netif_receive_skb(struct sk_buff *skb)
>>> if (netpoll_receive_skb(skb))
>>> return NET_RX_DROP;
>>>
>>> - __this_cpu_inc(softnet_data.processed);
>>> + skb->skb_iif = skb->dev->ifindex;
>>> + orig_dev = skb->dev;
>>
>> orig_dev should be set inside the loop, to reflect "previously
>> crossed device", while following the path:
>>
>> eth0 -> bond0 -> br0.
>>
>> First step inside loop:
>>
>> orig_dev = eth0
>> skb->dev = bond0 (at the end of the loop).
>>
>> Second step inside loop:
>>
>> orig_dev = bond0
>> skb->dev = br0 (et the end of the loop).
>>
>> This would allow for exact match delivery to bond0 if someone bind there.
>>
>>> +
>>> skb_reset_network_header(skb);
>>> skb_reset_transport_header(skb);
>>> skb->mac_len = skb->network_header - skb->mac_header;
>>> @@ -3138,12 +3141,9 @@ static int __netif_receive_skb(struct sk_buff *skb)
>>>
>>> rcu_read_lock();
>>>
>>> - if (!skb->skb_iif) {
>>> - skb->skb_iif = skb->dev->ifindex;
>>> - orig_dev = skb->dev;
>>> - } else {
>>> - orig_dev = dev_get_by_index_rcu(dev_net(skb->dev), skb->skb_iif);
>>> - }
>>
>> I like the fact that it removes the above part.
>>
>>> +another_round:
>>> + __this_cpu_inc(softnet_data.processed);
>>> + dev = skb->dev;
>>>
>>> #ifdef CONFIG_NET_CLS_ACT
>>> if (skb->tc_verd& TC_NCLS) {
>>> @@ -3153,7 +3153,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
>>> #endif
>>>
>>> list_for_each_entry_rcu(ptype,&ptype_all, list) {
>>> - if (!ptype->dev || ptype->dev == skb->dev) {
>>> + if (!ptype->dev || ptype->dev == dev) {
>>> if (pt_prev)
>>> ret = deliver_skb(skb, pt_prev, orig_dev);
>>> pt_prev = ptype;
>>
>> Inside the loop, we should only do exact match delivery, for
>> &ptype_all and for&ptype_base[ntohs(type)& PTYPE_HASH_MASK]:
>>
>> list_for_each_entry_rcu(ptype,&ptype_all, list) {
>> - if (!ptype->dev || ptype->dev == dev) {
>> + if (ptype->dev == dev) {
>> if (pt_prev)
>> ret = deliver_skb(skb, pt_prev, orig_dev);
>> pt_prev = ptype;
>> }
>> }
>>
>>
>> list_for_each_entry_rcu(ptype,
>> &ptype_base[ntohs(type)& PTYPE_HASH_MASK], list) {
>> if (ptype->type == type&&
>> - (ptype->dev == null_or_dev || ptype->dev == skb->dev)) {
>> + (ptype->dev == skb->dev)) {
>> if (pt_prev)
>> ret = deliver_skb(skb, pt_prev, orig_dev);
>> pt_prev = ptype;
>> }
>> }
>>
>> After leaving the loop, we can do wilcard delivery, if skb is not NULL.
>>
>> list_for_each_entry_rcu(ptype,&ptype_all, list) {
>> - if (!ptype->dev || ptype->dev == dev) {
>> + if (!ptype->dev) {
>> if (pt_prev)
>> ret = deliver_skb(skb, pt_prev, orig_dev);
>> pt_prev = ptype;
>> }
>> }
>>
>>
>> list_for_each_entry_rcu(ptype,
>> &ptype_base[ntohs(type)& PTYPE_HASH_MASK], list) {
>> - if (ptype->type == type&&
>> - (ptype->dev == null_or_dev || ptype->dev == skb->dev)) {
>> + if (ptype->type == type&& !ptype->dev) {
>> if (pt_prev)
>> ret = deliver_skb(skb, pt_prev, orig_dev);
>> pt_prev = ptype;
>> }
>> }
>>
>> This would reduce the number of tests inside the
>> list_for_each_entry_rcu() loops. And because we match only ptype->dev
>> == dev inside the loop and !ptype->dev outside the loop, this should
>> avoid duplicate delivery.
>
> Would you care to put this into patch so I can see the whole picture?
> Thanks.
Here is what I have in mind. It is based on your previous DRAFT patch, and don't modify rx_handlers yet.
Only compile tested !!
I don't know if every pieces are at the right place. I wonder what to do with CONFIG_NET_CLS_ACT
part, that currently is between ptype_all and ptype_base processing.
Anyway, the general idea is there.
Nicolas.
net/core/dev.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 60 insertions(+), 10 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index e5dba47..7e007a9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3117,7 +3117,6 @@ static int __netif_receive_skb(struct sk_buff *skb)
rx_handler_func_t *rx_handler;
struct net_device *dev;
struct net_device *orig_dev;
- struct net_device *null_or_dev;
int ret = NET_RX_DROP;
__be16 type;
@@ -3130,9 +3129,6 @@ static int __netif_receive_skb(struct sk_buff *skb)
if (netpoll_receive_skb(skb))
return NET_RX_DROP;
- skb->skb_iif = skb->dev->ifindex;
- orig_dev = skb->dev;
-
skb_reset_network_header(skb);
skb_reset_transport_header(skb);
skb->mac_len = skb->network_header - skb->mac_header;
@@ -3143,6 +3139,8 @@ static int __netif_receive_skb(struct sk_buff *skb)
another_round:
__this_cpu_inc(softnet_data.processed);
+ skb->skb_iif = skb->dev->ifindex;
+ orig_dev = skb->dev;
dev = skb->dev;
#ifdef CONFIG_NET_CLS_ACT
@@ -3152,8 +3150,13 @@ another_round:
}
#endif
+ /*
+ * Deliver to ptype_all protocol handlers that match current dev.
+ * This happens before rx_handler is given a chance to change skb->dev.
+ */
+
list_for_each_entry_rcu(ptype, &ptype_all, list) {
- if (!ptype->dev || ptype->dev == dev) {
+ if (ptype->dev == dev) {
if (pt_prev)
ret = deliver_skb(skb, pt_prev, orig_dev);
pt_prev = ptype;
@@ -3167,6 +3170,31 @@ another_round:
ncls:
#endif
+ /*
+ * Deliver to ptype_base protocol handlers that match current dev.
+ * This happens before rx_handler is given a chance to change skb->dev.
+ */
+
+ type = skb->protocol;
+ list_for_each_entry_rcu(ptype,
+ &ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
+ if (ptype->type == type && ptype->dev == skb->dev) {
+ if (pt_prev)
+ ret = deliver_skb(skb, pt_prev, orig_dev);
+ pt_prev = ptype;
+ }
+ }
+
+ /*
+ * Call rx_handler for current device.
+ * If rx_handler return NULL, skip wilcard protocol handler delivery.
+ * Else, if skb->dev changed, restart the whole delivery process, to
+ * allow for device nesting.
+ *
+ * Warning:
+ * rx_handlers must kfree_skb(skb) if they return NULL.
+ */
+
rx_handler = rcu_dereference(dev->rx_handler);
if (rx_handler) {
if (pt_prev) {
@@ -3176,10 +3204,15 @@ ncls:
skb = rx_handler(skb);
if (!skb)
goto out;
- if (dev != skb->dev)
+ if (skb->dev != dev)
goto another_round;
}
+ /*
+ * FIXME: The part below should use rx_handler instead of being hard
+ * coded here.
+ */
+
if (vlan_tx_tag_present(skb)) {
if (pt_prev) {
ret = deliver_skb(skb, pt_prev, orig_dev);
@@ -3192,16 +3225,33 @@ ncls:
goto out;
}
+ /*
+ * FIXME: Can't this be moved into the rx_handler for bonding,
+ * or into a futur rx_handler for vlan?
+ */
+
vlan_on_bond_hook(skb);
- /* deliver only exact match when indicated */
- null_or_dev = skb->deliver_no_wcard ? skb->dev : NULL;
+ /*
+ * Deliver to wildcard ptype_all protocol handlers.
+ */
+
+ list_for_each_entry_rcu(ptype, &ptype_all, list) {
+ if (!ptype->dev) {
+ if (pt_prev)
+ ret = deliver_skb(skb, pt_prev, orig_dev);
+ pt_prev = ptype;
+ }
+ }
+
+ /*
+ * Deliver to wildcard ptype_all protocol handlers.
+ */
type = skb->protocol;
list_for_each_entry_rcu(ptype,
&ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
- if (ptype->type == type &&
- (ptype->dev == null_or_dev || ptype->dev == skb->dev)) {
+ if (ptype->type == type && !ptype->dev) {
if (pt_prev)
ret = deliver_skb(skb, pt_prev, orig_dev);
pt_prev = ptype;
--
1.7.2.3
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