netdev - Re: Multicast packet loss

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Date:	Tue, 17 Mar 2009 22:19:58 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	David Stevens <dlstevens@...ibm.com>
CC:	Brian Bloniarz <bmb@...enacr.com>, cl@...ux-foundation.org,
	David Miller <davem@...emloft.net>, kchang@...enacr.com,
	netdev@...r.kernel.org, netdev-owner@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: Multicast packet loss

David Stevens a écrit :
> I did some testing with this and see at least a 20% improvement
> without drop.
> 
> I agree with Peter's recommended changes (esp. sentinel vs null),
> and also the trivial brace indentation  in softirq_delay_exec(),
> but otherwise looks  good to me. Nice work.
> 
>                                         +-DLS
> 
> 

Still I dont like very much all softirq.c changes. I feel very
uncomfortable to justify one extra call in do_softirq(), and
not very clean interface (stuff about locking, barriers...)

Easy way could be to add a SOFTIRQ but its not very wise.

I was wondering if we could use the infrastructure added in commit
54514a70adefe356afe854e2d3912d46668068e6
(softirq: Add support for triggering softirq work on softirqs.)
But I dont understand how it can works...
(softirq_work_list is feeded, but never processed)

Alternatively, we could use a framework dedicated to
network use, with well defined semantic :

Calling softirq_delay_exec() from net_rx_action(),
from this function, we know if time_squeeze was incremented,
or all netdev_budget consumed, and in this stress case 
try to give the wakeups job to another cpu.

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