netdev - RE: [PATCH net-next 3/9] net: Remove e_nobufs label from ip_route_input

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Date:	Thu, 24 Sep 2015 10:53:23 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	"'Eric W. Biederman'" <ebiederm@...ssion.com>,
	David Ahern <dsa@...ulusnetworks.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 3/9] net: Remove e_nobufs label from
 ip_route_input_slow

From: Eric W. Biederman
> Sent: 23 September 2015 03:15
> David Ahern <dsa@...ulusnetworks.com> writes:
> 
> > e_nobufs has 1 user. Move setting err to -ENOBUFS for the 1 user and
> > use the goto out label instead of e_nobufs. Stepping stone patch; next
> > one moves rth code into a helper function.
> 
> Ick you are pessimizing the code.
> 
> You will almost certainly have better code generation if you hoist
> the assignment of "err = -ENOBUFS" above the rt_dst_alloc then you
> don't need to do anything in your error path except "goto out;"

Unlikely to make a difference.
The compiler is very likely to set 'err' before the conditional
branch anyway. It will use an extra register to make it all work.

	David

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