Re: [PATCH net-next 1/2] tcp/dccp: Move initialisation of refcounted into if block.

Eric Dumazet <[email protected]>
Newsgroups org.kernel.vger.dccp,org.kernel.vger.netdev
Message-ID <CANn89iJzxqF8j6uUO9BqmMY0tVh+intVj-v-tygXc_8r6-wjkg@mail.gmail.com>
On Mon, Mar 23, 2020 at 11:18 AM Kuniyuki Iwashima <[email protected]> wrote:
>
> The refcounted is initialised at most three times.
>
>   - __inet_lookup_skb() sets it true.
>   - skb_steal_sock() is false and __inet_lookup() sets it true.
>   - __inet_lookup_established() is false and __inet_lookup() sets it false.
>
> We do not need to initialise refcounted again and again, so we should do
> it just before return.
>
> Signed-off-by: Kuniyuki Iwashima <[email protected]>
> ---

Well, I do not believe this patch (and the following one) makes things
more readable.

I doubt setting a boolean in a register or a stack variable has any cost,
I prefer letting the compiler optimize this.

The ehash lookup cost is at least 2 or 3 cache lines, this is the
major contribution.
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