Date: Sat, 25 Sep 2010 10:20:19 +0200 From: Andre Oppermann <andre@freebsd.org> To: Julian Elischer <julian@freebsd.org> Cc: FreeBSD Net <net@freebsd.org> Subject: Re: mbuf changes Message-ID: <4C9DB0C3.5010601@freebsd.org> In-Reply-To: <4C9DA26D.7000309@freebsd.org> References: <4C9DA26D.7000309@freebsd.org>
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On 25.09.2010 09:19, Julian Elischer wrote: > over the last few years there has been a bit of talk about some changes people want to see in mbufs > for 9.x > extra fields, changes in the way things are done, etc. > > If you are one of these people, pipe up now.. > > to get the ball rolling.. > > * Add a field for the current FIB.. currently this is 4 bits stolen from the flags. > what would be a good width: 8,12,16,24,32 bits? > this would allow setfib to use numbers greater than 16 (the current max) 16 bits for 65535 FIB's should be sufficient. More than that seems really excessive. > * Preallocating some room for some number of tags before we start allocating > (expensively) new ones. Within the mbuf? Or at external and attached mbuf allocation time? Tags are variable width and such not really suitable for pre-allocation. > * dynamically working out what the front padding size should be.. per session.. i.e. > when a packet is sent out and needs to be adjusted to add more headers, the originating > socket should be notified, or maybe the route should have this information... > so that future packets can start out with enough head room. > (this is not strictly to do with mbufs but might need some added field to point to the structure > that needs to be > updated. We already have "max_linkhdr" that specifies how much space is left for prepends at the start of each packet. The link protocols set this and also IPSec adds itself in there if enabled. If you have other encapsulations you should make them add in there as well. -- Andre
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