Date: Thu, 2 Nov 2006 18:11:00 -0500 From: "Devon H. O'Dell" <devon.odell@gmail.com> To: hackers@freebsd.org Subject: vr(4) performance Message-ID: <9ab217670611021511l3120d58bhd0b61bf44f8ecc87@mail.gmail.com>
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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'') Kind regards, Devon H. O'Dell
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