On 08/30/2016 08:00 PM, Tom Herbert wrote:
XFS maintains a per device flow table that is indexed by the skbuff
hash. The XFS table is only consulted when there is no queue saved in
a transmit socket for an skbuff.
Each entry in the flow table contains a queue index and a queue
pointer. The queue pointer is set when a queue is chosen using a
flow table entry. This pointer is set to the head pointer in the
transmit queue (which is maintained by BQL).
The new function get_xfs_index that looks up flows in the XPS table.
The entry returned gives the last queue a matching flow used. The
returned queue is compared against the normal XPS queue. If they
are different, then we only switch if the tail pointer in the TX
queue has advanced past the pointer saved in the entry. In this
way OOO should be avoided when XPS wants to use a different queue.
I'd love for Dave Chinner to get some networking bug reports, but maybe
we shouldn't call it XFS?
At least CONFIG_XFS should be something else. It doesn't conflict now
because we have CONFIG_XFS_FS, but even CONFIG_XFS_NET sounds like it's
related to the filesystem instead of transmit flows.
[ Sorry, four patches in and all I do is complain about the name ]
-chris
Signed-off-by: Tom Herbert <t...@herbertland.com>
---
net/Kconfig | 6 ++++
net/core/dev.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++----------
2 files changed, 84 insertions(+), 15 deletions(-)
diff --git a/net/Kconfig b/net/Kconfig
index 7b6cd34..5e3eddf 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -255,6 +255,12 @@ config XPS
depends on SMP
default y
+config XFS
+ bool
+ depends on XPS
+ depends on BQL
+ default y
+
config HWBM
bool
...
-static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
+/* Must be called with RCU read_lock */
+static int get_xfs_index(struct net_device *dev, struct sk_buff *skb)
{
- struct sock *sk = skb->sk;
- int queue_index = sk_tx_queue_get(sk);
+#ifdef CONFIG_XFS
+ struct xps_dev_flow_table *flow_table;
+ struct xps_dev_flow ent;
+ int queue_index;
+ struct netdev_queue *txq;
+ u32 hash;
