netdev - Re: [PATCH net-next 1/2] net: updating dst lastusage is an unlikely event.

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Message-ID: <1508841585.2758.10.camel@redhat.com>
Date:   Tue, 24 Oct 2017 12:39:45 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Wei Wang <weiwan@...gle.com>, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH net-next 1/2] net: updating dst lastusage is an unlikely
 event.

On Tue, 2017-10-24 at 12:37 +0200, Paolo Abeni wrote:
> Since commit 0da4af00b2ed ("ipv6: only update __use and lastusetime
> once per jiffy at most"), updating the dst lastuse field is an
> unlikely action: it happens at most once per jiffy, out of
> potentially millions of calls per second.
> 
> Mark explicitly the code as such, and let the compiler generate
> better code.
> 
> Note: gcc 7.2 and several older versions do actually generate
> different - better - code when the unlikely() hint is in place,
> avoid jump in the fast path and keeping better code locality.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Oops, I placed a bad subject prefix here, please ignore. I'll resend
soon with a proper one.

Sorry for the noise,

Paolo