On Thu, Nov 02, 2006 at 03:27:46PM -0800, Sam Leffler wrote: > Devon H. O'Dell wrote: > > Hey all, > > > > So, vr(4) kind of sucks, and it seems like this is mostly due to the > > fact that we call m_defrag() on every mbuf that we send through it. > > This seems to really screw performance on outgoing packets (something > > like 33% the output efficiency of fxp(4), if I'm understanding this > > all correctly). > > > > I'm sort of wondering if anybody has attempted to address this before > > and if there's a way to possibly mitigate this behavior. I know Bill > > Paul's comments say ``Unfortunately, FreeBSD FreeBSD doesn't guarantee > > that mbufs will be filled in starting at longword boundaries, so we > > have to do a buffer copy before transmission.'' -- since it's been a > > long day, and I'm about to go home to grab a pizza and stop thinking > > about code, would anybody mind offering suggestions as to either: > > > > a) Pros and cons of guaranteeing that they're filled in aligned (and > > possibly hints on doing it), or > > b) Possible workarounds / hacks to do this faster for vr(4) > > > > Any input is appreciated! (Except ``vr(4) is lol'') > > m_defrag is ~10x slower than it needs to be. I proposed changes to > address this a while back but eventually gave up and put driver-specific > code in ath. You can look there or I can send you some patches to > m_defrag to try out in vr. >
Because the purpose of m_defrag(9) in vr(4) is to guarantee longword aligned mbufs I'm not sure ath_defrag can be used here. If memory serve me right ath_defrag would not change the first mbuf address in a chain. If the first mbuf is not aligned on longword boundary it wouldn't work I guess. Of course we can check the first mbuf in the chain before calling super-fast ath_defrag, I guess. -- Regards, Pyun YongHyeon _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
