Andrew, On Wed, Oct 19, 2005 at 11:25:59PM +1300, Andrew Thompson wrote: A> It has always bugged me how the vlan code traverses the linked-list for A> each incoming packet to find the right ifvlan, I have this patch which A> attempts to fix this. A> A> What it does is replace the linear search for the vlan with a constant A> time lookup. It does this by allocating an array for each vlan enabled A> parent interface so the tag can be directly indexed. A> A> This has an overhead of ~16kb on 32bit, this is not too bad as there is A> usually only one physical interface when using a large number of vlans. A> A> I have measured a 1.6% pps increase with 100 vlans, and 8% with 500, and A> yes, some people use this many in production. A> A> It also has the benefit of enforcing unique vlan tags per parent which A> the current code doesn't do.
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. -- Totus tuus, Glebius. GLEBIUS-RIPN GLEB-RIPE _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
