This set of patches implements the batching xmit capability, and adds support
for batching in IPoIB and E1000 (E1000 driver changes is ported, thanks to
changes taken from Jamal's code from an old kernel).
List of changes from previous revision:
----------------------------------------
1. [Dave] Enable batching as default (change in register_netdev).
2. [Randy] Update documentation (however ethtool cmd to get/set batching is
not implemented, hence I am guessing the usage).
3. [KK] When changing tx_batch_skb, qdisc xmits need to be blocked since
qdisc_restart() drops queue_lock before calling driver xmit, and
driver could find blist change under it.
4. [KK] sched: requeue could wrongly requeue skb already put in the batching
list (in case a single skb was sent to the device but not sent as the
device was full, resulting in the skb getting added to blist). This
also results in slight optimization of batching behavior where for
getting skbs #2 onwards don't require to check for gso_skb as that
is the first skb that is processed.
4. [KK] Change documentation to explain this behavior.
5. [KK] sched: Fix panic when GSO is enabled in driver.
6. [KK] IPoIB: Small optimization in ipoib_ib_handle_tx_wc
7. [KK] netdevice: Needed to change NETIF_F_GSO_SHIFT/NETIF_F_GSO_MASK as
BATCH_SKBS is now defined as 65536 (earlier it was using 8192 which
was taken up by NETIF_F_NETNS_LOCAL).
Will submit in the next 1-2 days:
---------------------------------
1. [Auke] Enable batching in e1000e.
Extras that I can do later:
---------------------------
1. [Patrick] Use skb_blist statically in netdevice. This could also be used
to integrate GSO and batching.
2. [Evgeniy] Useful to splice lists dev_add_skb_to_blist (and this can be
done for regular xmit's of GSO skbs too for #1 above).
Patches are described as:
Mail 0/10: This mail
Mail 1/10: HOWTO documentation
Mail 2/10: Introduce skb_blist, NETIF_F_BATCH_SKBS, use
single API for batching/no-batching, etc.
Mail 3/10: Modify qdisc_run() to support batching
Mail 4/10: Add ethtool support to enable/disable batching
Mail 5/10: IPoIB: Header file changes to use batching
Mail 6/10: IPoIB: CM & Multicast changes
Mail 7/10: IPoIB: Verbs changes to use batching
Mail 8/10: IPoIB: Internal post and work completion handler
Mail 9/10: IPoIB: Implement the new batching capability
Mail 10/10: E1000: Implement the new batching capability
Issues:
--------
The retransmission problem reported earlier seems to happen when mthca is
used as the underlying device, but when I tested ehca the retransmissions
dropped to normal levels (around 2 times the regular code). The performance
improvement is around 55% for TCP.
Please review and provide feedback; and consider for inclusion.
Thanks,
- KK
----------------------------------------------------
TCP
----
Size:32 Procs:1 2728 3544 29.91
Size:128 Procs:1 11803 13679 15.89
Size:512 Procs:1 43279 49665 14.75
Size:4096 Procs:1 147952 101246 -31.56
Size:16384 Procs:1 149852 141897 -5.30
Size:32 Procs:4 10562 11349 7.45
Size:128 Procs:4 41010 40832 -.43
Size:512 Procs:4 75374 130943 73.72
Size:4096 Procs:4 167996 368218 119.18
Size:16384 Procs:4 123176 379524 208.11
Size:32 Procs:8 21125 21990 4.09
Size:128 Procs:8 77419 78605 1.53
Size:512 Procs:8 234678 265047 12.94
Size:4096 Procs:8 218063 367604 68.57
Size:16384 Procs:8 184283 370972 101.30
Average: 1509300 -> 2345115 = 55.38%
----------------------------------------------------
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