Re: [B.A.T.M.A.N.] [PATCH] batman-adv: Deinline batadv_orig_hash_find, save 9024 bytes

Antonio Quartulli
2016-04-25T14:19:41Z

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On Mon, Apr 25, 2016 at 03:45:20PM +0200, Denys Vlasenko wrote:
> On 04/25/2016 03:39 PM, Antonio Quartulli wrote:
> > On Mon, Apr 25, 2016 at 03:25:22PM +0200, Denys Vlasenko wrote:
> >> This function compiles to 473 bytes of machine code.
> >> 21 callsites.
> >>
> >> text data bss dec hex filename
> >> 95903266 20860288 35991552 152755106 91adba2 vmlinux_before
> >> 95894242 20860288 35991552 152746082 91ab862 vmlinux
> >
> > Hi Danys,
> >
> > thanks for your patch. This function is used in a several performance critical
> > code paths (i.e. packet forwarding).
> >
> > Are we sure we are not losing in performance here?
>
> Is this a common case?
>
> if (!hash)
> return NULL;
>
> If yes, then we can inline this part only.

Unfortunately not: this case is rather rare at runtime.
These hash tables are initialized when the batman virtual interface is created
and should be freed only upon interface shutdown.

(actually I believe this might be a good candidate for an unlikely())

Cheers,

--
Antonio Quartulli

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