Date: Fri, 29 Sep 2006 19:11:56 -0400 From: Randall Stewart <rrs@cisco.com> To: John-Mark Gurney <gurney_j@resnet.uoregon.edu> Cc: freebsd-net@freebsd.org, freebsd-current@freebsd.org, Andre Oppermann <andre@freebsd.org>, gallatin@cs.duke.edu Subject: Re: Much improved sosend_*() functions Message-ID: <451DA83C.4050808@cisco.com> In-Reply-To: <20060929231007.GS80527@funkthat.com> References: <451C4850.5030302@freebsd.org> <Pine.BSF.4.58.0609281928020.20971@niwun.pair.com> <451D884F.1030807@cisco.com> <20060929213722.GR80527@funkthat.com> <451D973C.8070004@freebsd.org> <20060929231007.GS80527@funkthat.com>
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John-Mark Gurney wrote: > Andre Oppermann wrote this message on Fri, Sep 29, 2006 at 23:59 +0200: > >>>w/ 512 byte mbuf and a 2k cluster just to store just 1514 bytes of data, >>>that's only 60% effeciency wrt to memory usage... so, we currently >>>waste 40% of memory allocated to mbufs+clusters... Even reducing >>>mbufs back to 128 or 256 would be a big help, though IPSEC I believe >>>would have issues... >> >>mbufs are 256 bytes. > > > Hmmm.. I keep getting this confused... maybe because there was discussion > about increasing this a few years back... or maybe because NOTES has > it as 512.. :) > > >>>Hmmm.. If we switched clusters to 1536 bytes in size, we'd be able to >>>fit 8 in 12k (though I guess for 8k page boxes we'd do 16 in 24k)... The >>>only issue w/ that would be that a few of the clusters would possibly >>>split page boundaries... How much this would effect performance would >>>be an interesting question to answer... >> >>Splitting page boundaries is not an option as it may not be physically >>contigous. > > > unless we do something strange like allocate them contigously... though > that introduces another set of issues.... > > >>Just don't overengineer the stuff. Mbufs are only used temporarily and >>a bit theoretical waste is not much a problem (so far at least). > > > Well, I beg to differ... most gige cards grab mbuf+cluster for every > single ring buffer they have.. which is usually 512... so every gige > interface for the most part consumes 1meg of memory that is not > reusable... because if we run out of mbuf+clusters to replace in the > receive ring, we will not tap into the 1meg of mbuf+clusters available > to us... so, if you have a quad gige, that's 4megs wasted, plus w/ the > fact that we could only use ~65% of that memory, that's a lot of memory > wasted... > > Yeh, everyone says you have gigs of memory, but do we really want to > be known as the wasteful OS? > Let me try to find some cycles (somewhere) and play with this :-) R -- Randall Stewart NSSTG - Cisco Systems Inc. 803-345-0369 <or> 815-342-5222 (cell)
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