[ofa-general] Re: [PATCH 02/10] Networking include file changes.

Hi Sridhar,

Sridhar Samudrala [off-list ref] wrote on 07/23/2007 11:29:39 AM:

Krishna Kumar2 wrote:

quoted

Hi Sridhar,

Sridhar Samudrala [off-list ref] wrote on 07/20/2007 10:55:05 PM:

quoted

quoted

diff -ruNp org/include/net/pkt_sched.h new/include/net/pkt_sched.h

--- org/include/net/pkt_sched.h   2007-07-20 07:49:28.000000000 +0530
+++ new/include/net/pkt_sched.h   2007-07-20 08:30:22.000000000 +0530

@@ -80,13 +80,13 @@ extern struct qdisc_rate_table *qdisc_ge
       struct rtattr *tab);
 extern void qdisc_put_rtab(struct qdisc_rate_table *tab);

-extern void __qdisc_run(struct net_device *dev);
+extern void __qdisc_run(struct net_device *dev, struct sk_buff_head

*blist);

quoted

Why do we need this additional 'blist' argument?
Is this different from dev->skb_blist?

It is the same, but I want to call it mostly with NULL and rarely with

the

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batch list pointer (so it is related to your other question). My

original

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code didn't have this and was trying batching in all cases. But in most
xmit's (probably almost all), there will be only one packet in the

queue to

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send and batching will never happen. When there is a lock contention or

if

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the queue is stopped, then the next iteration will find >1 packets. But

I

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still will try no batching for the lock failure case as there be

probably

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2 packets (one from previous time and 1 from this time, or 3 if two
failures,
etc), and try batching only when queue was stopped from net_tx_action

(this

quoted

was based on Dave Miller's idea).

Is this right to say that the above change is to get this behavior?
   If qdisc_run() is called from dev_queue_xmit() don't use batching.
   If qdisc_run() is called from net_tx_action(), do batching.

Correct.

Isn't it possible to have multiple skb's in the qdisc queue in the
first case?

It is possible but rarer (so unnecessary checking most of the time). From
net_tx_action you are guaranteed to have multiple skbs, but from xmit you
will almost always get one skb (since most send of 1 skb will go out OK).
And also in the xmit path, it is more likely to have few skbs compared to
possibly hundreds in the net_tx_action path.

If this additional argument is used to indicate if we should do batching
or not, then passing a flag may be much more cleaner than passing the

blist.

OK, I will add this as another action item to check (along with Patrick's
suggestion to use single API) and will get back.

- KK