Date: Thu, 20 Oct 2005 16:21:52 +0400 From: Yar Tikhiy <yar@comp.chem.msu.su> To: Ragnar Lonn <raglon@packetfront.com> Cc: freebsd-net@FreeBSD.org, Gleb Smirnoff <glebius@FreeBSD.org>, ru@FreeBSD.org, Andrew Thompson <thompsa@FreeBSD.org> Subject: Re: vlan patch Message-ID: <20051020122151.GB47217@comp.chem.msu.su> In-Reply-To: <43575A74.6090004@packetfront.com> References: <20051019102559.GA45909@heff.fud.org.nz> <20051020070054.GZ59364@cell.sick.ru> <43575A74.6090004@packetfront.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Oct 20, 2005 at 10:51:00AM +0200, Ragnar Lonn wrote: > Gleb Smirnoff wrote: > > >Although the memory overhead is not noticable on modern i386 and amd64 > >PCs I don't think that we should waste so much memory. We should keep > >in mind the existence of embedded architectures with little memory. > > > >In most cases people use 10 - 30 VLANs. I suggest to use a hash, like it > >is already done in ng_vlan(4). This hash makes every sixteenth VLAN to fall > >into same slot. Since most people allocate VLAN ids contiguously the hash > >distribution should be good. > > > >Moreover, I suggest Yar and Ruslan to work together and make the hash code > >shared between vlan(4) and ng_vlan(4), not copy-and-pasted. > > It looks as if ng_vlan implements a standard hash. Wouldn't a hashtree > be a good > compromise between speed and memory usage? Of course, a 16-slot hash is > a lot > better than no hash at all :-) The only problem with the hash currently used in ng_vlan is that it is fixed-width. I think it will be easy to teach it how to cope with variable bit-width of hash using the same xor-folding technique. I hope I'll have free time this week-end to test the performance of the approaches discussed since implementing them is no problem at all. -- Yar
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20051020122151.GB47217>