Message-ID: <1361206302.8555.36.camel@jlt4.sipsolutions.net> (sfid-20130218_175153_283892_34CE126A)
Subject: Re: [RFC] design discussion: Collecting information for (non-peer)
 stations
From: Johannes Berg <johannes@sipsolutions.net>
To: Antonio Quartulli <antonio@open-mesh.com>
Cc: Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	Thomas Pedersen <thomas@cozybit.com>,
	Marek Lindner <marek@open-mesh.com>,
	Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
Date: Mon, 18 Feb 2013 17:51:42 +0100
In-Reply-To: <20130218160705.GD4162@open-mesh.com>
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On Mon, 2013-02-18 at 17:07 +0100, Antonio Quartulli wrote:
> On Mon, Feb 18, 2013 at 07:58:18 -0800, Johannes Berg wrote:
> > On Mon, 2013-02-18 at 16:49 +0100, Antonio Quartulli wrote:
> > > On Mon, Feb 18, 2013 at 07:43:26 -0800, Johannes Berg wrote:
> > > > > I did not like this approach because the sta_info struct is so big that
> > > > > when we want to fill the stats substruct only we will waste a lot of bytes.
> > > > 
> > > > I don't understand your point.
> > > > 
> > > > struct sta_info {
> > > >    ...
> > > >    struct stats stats;
> > > > };
> > > 
> > > My concern is about those "..." that we are allocating within the sta_info struct
> > > that we will never use for every non-peer station.
> > > 
> > > While if we used the struct below (with its own hash table), we would allocate
> > > only the space needed for the stats.
> > > 
> > > > 
> > > > struct stats_entry {
> > > >    struct hash/list/whatever;
> > > >    struct stats stats;
> > > > };
> > > > 
> > > 
> > > 
> > > no?
> > > Maybe I misunderstood your idea?
> > 
> > But I'm not saying that these are mutually exclusive, I'm saying both
> > should exist.
> 
> Ah ok..Sorry, but I did not take this as an option :)
> 
> So, if I understood correctly, this means one table lookup for peer stations,
> while two table lookups for non peers (first in sta_hash, which will fail). Right?
> 
> This would save one look up for each peer, since we have to do perform one of
> them anyway (now I fully understood your previous statement!).

Right... But the failing sta lookup has to happen anyway, so it really
adds practically no cost in the peer case, and a singe lookup in the
"non-peer already exists" case.

johannes