netdev - Re: [PATCH] pktgen: nowait parameter.

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Message-Id: <20140905.142618.2240630803375505977.davem@davemloft.net>
Date:	Fri, 05 Sep 2014 14:26:18 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	rusty@...tcorp.com.au
Cc:	netdev@...r.kernel.org, brouer@...hat.com, minipli@...glemail.com
Subject: Re: [PATCH] pktgen: nowait parameter.

From: Rusty Russell <rusty@...tcorp.com.au>
Date: Wed, 03 Sep 2014 13:50:01 +0930

> While trying to measure speed of virtio_net, I was getting hangs.
> This is because we skb_orphan() but delay the tx interrupt
> indefinitely (by number of slots).
> 
> With nowait, pktgen won't wait for the skb to be released.  This
> introduces an error, but it's ok if count >> ringsize.
> 
> I updated the documentation, but it needs far more work (it
> refers to pgset and an examples directory, none of which exist
> in the kernel tree).
> 
> Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

Please just make this a flag, like UDPCSUM, NO_TIMESTAMP, et al.
Which also means that it should be capitalized.

BTW, wrt. holding onto TX frames for unbounded amounts of time, I
think this is a bad idea even with skb_orphan().  There are resources
from the SKB you are hanging onto which can stall the removal of
modules indefinitely, such as netfilter references.
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