Date: Fri, 12 Jul 2002 21:37:37 -0400 From: Bosko Milekic <bmilekic@unixdaemons.com> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: Julian Elischer <julian@elischer.org>, freebsd-net@FreeBSD.ORG Subject: Re: mbuf external buffer reference counters Message-ID: <20020712213737.A7548@unixdaemons.com> In-Reply-To: <15663.24169.445698.304534@grasshopper.cs.duke.edu>; from gallatin@cs.duke.edu on Fri, Jul 12, 2002 at 06:55:37PM -0400 References: <20020712122811.GA52803@hades.hell.gr> <Pine.BSF.4.21.0207121108270.50700-100000@InterJet.elischer.org> <15663.24169.445698.304534@grasshopper.cs.duke.edu>
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On Fri, Jul 12, 2002 at 06:55:37PM -0400, Andrew Gallatin wrote: [...] FWIW, BSD/OS also does similar to -STABLE. [...] > I agree with John about where to put the refcnts: I think we should > have a big hunk of memory for the refcnts like in -stable. My > understanding is that the larger virtually contig mbufs are the only > thing that would cause a problem for this, or is that incorrect? > If so, then why not just put their counter elsewhere? > > One concrete example against putting the refcnts into the cluster is > that it would cause NFS servers & clients to use 25% more mbufs for a > typical 8K read or write request. If we decide to allocate jumbo bufs from their own seperate map as well then we have no wastage for the counters for clusters if we keep them in a few pages, like in -STABLE, and it should all work out fine. For the jumbo bufs I still maintain that we should keep the counter for them at the end of the buf because the math works out (see my post in that thread with the math example) and because their total size is not a power of 2 anyway. They'll also be more randomly spread out and use more cache slots. > Drew Regards, -- Bosko Milekic bmilekic@unixdaemons.com bmilekic@FreeBSD.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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