From: Stephen Hemminger <shemminger@vyatta.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>, netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH] ipv4: IP defragmentation must be ECN aware
Date: Wed, 5 Jan 2011 09:48:30 -0800 [thread overview]
Message-ID: <20110105094830.63a68230@nehalam> (raw)
In-Reply-To: <1294249261.10633.54.camel@edumazet-laptop>
On Wed, 05 Jan 2011 18:41:01 +0100
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Le mercredi 05 janvier 2011 à 09:13 -0800, Stephen Hemminger a écrit :
> > On Wed, 05 Jan 2011 14:59:02 +0100
> > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >
> > > +
> > > +static inline int ip4_frag_ecn(int tos)
> >
> > Since tos is only a byte, this should be:
> >
> > static inline u8 ip4_frag_ecn(u8 tos)
> >
> >
>
> In fact, generated code is the same on x86, but some arches have faster
> arithmetic on WORD units.
>
> And I added the 'inline' because on x86_64 gcc, compiler chose _not_ to
> inline this 6 instruction sequence ! Code was much larger.
>
> 31 d2 xor %edx,%edx
> 0f b6 40 01 movzbl 0x1(%rax),%eax
> 83 e0 03 and $0x3,%eax
> ff c0 inc %eax
> a8 02 test $0x2,%al
> 0f 44 d0 cmove %eax,%edx
>
>
> We do roughly the same (working on WORD arith) in
>
At least make it unsigned int?
--
next prev parent reply other threads:[~2011-01-05 17:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-05 0:13 [RFC] ECN and IP defragmentation Eric Dumazet
2011-01-05 2:53 ` David Miller
2011-01-05 13:59 ` [PATCH] ipv4: IP defragmentation must be ECN aware Eric Dumazet
2011-01-05 17:13 ` Stephen Hemminger
2011-01-05 17:41 ` Eric Dumazet
2011-01-05 17:48 ` Stephen Hemminger [this message]
2011-01-05 17:52 ` Eric Dumazet
2011-01-06 19:21 ` David Miller
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