netdev - Re: TSO trimming question

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Message-Id: <20071221135437.16fa63c8.billfink@mindspring.com>
Date:	Fri, 21 Dec 2007 13:54:37 -0500
From:	Bill Fink <billfink@...dspring.com>
To:	Bill Fink <billfink@...dspring.com>
Cc:	David Miller <davem@...emloft.net>, herbert@...dor.apana.org.au,
	ilpo.jarvinen@...sinki.fi, netdev@...r.kernel.org, jheffner@....edu
Subject: Re: TSO trimming question

On Fri, 21 Dec 2007, Bill Fink wrote:

> Or perhaps even:
> 
> 	/* Ok, it looks like it is advisable to defer.  */
> 	tp->tso_deferred = jiffies;
> 
> 	/* need to return a non-zero value to defer, which means won't
> 	 * defer if jiffies == 0 but it's only a 1 in 4 billion event
> 	 * (and avoids a compare/branch by not checking jiffies)
> 	 /
>         return jiffies;

Ack.  I introduced my own 64-bit to 32-bit issue (too late at night).
How about:

	/* Ok, it looks like it is advisable to defer.  */
	tp->tso_deferred = jiffies;

	/* this won't defer if jiffies == 0 but it's only a 1 in
	 * 4 billion event (and avoids a branch)
	 */
	return (jiffies != 0);

							-Bill
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