2009/12/23 Gerald A <[email protected]>:
> Hi Tim,
> On Tue, Dec 22, 2009 at 10:29 PM, Tim Nelson <[email protected]> wrote:
>>
>> ----- "Gerald A" <[email protected]> wrote:
>> > Hey Tim,
>> > Adding RAM won't increase MBUFs, if I remember correctly. It is a kernel
>> > param, and can be tweaked by recompiling the kernel. (It may nowadays be
>> > possible to massage it by sysctl, or as a boot time param, but I'm not
>> > sure). So, you can tweak it without adding RAM.
>
> After a bit of research, I found that they had made this a sysctl:
>  sysctl kern.ipc.nmbclusters
> The example I found mentioned 65535 as a number, your mileage may vary.
>
>> > I've seen this when an ipfw rule prevented sending, like for a ping.
>> > Could it be a > fw rule that is causing this? (Just grasping at straws).
>>
>> Right now, it's just functioning as a 'core' router with NAT turned off.
>> All interfaces have "Allow any protocol from anywhere to anywhere" rules on
>> them. There are no other services enabled, not even dns forwarder or DHCP.
>> Just pure routing and RIP.
>>
>> Looking at my edge firewall, I see MBUF usage like this:  738 /1845 which
>> is very odd since that box also has 256MB RAM. The only difference is that
>> my edge box has 2x128MB DIMMs and my core (problematic box) has a single
>> 256MB DIMM. Are the MBUF values calculated randomly? Where do they come
>> from?
>
>
> I tried doing some research on this one, and wasn't as successful. From what
> I recall, there is some important constant somewhere in the kernel sources
> that sets this up initially. It might now additionally be sized by RAM or
> some other magic, and since it's a dynamic tunable, you can tweak it at
> boottime (or anytime).
> I'd be surprised if it was random. One thing you did mention was that your
> "core" box has 5 interfaces -- my off the cuff guess would be that mbufs are
> added as the number of interfaces increases. It would make sense, since you
> would potentially have more network traffic requiring more resources.
> Thanks,
> Gerald.

please look here, ind the section Loader Tunables:
http://www.freebsd.org/cgi/man.cgi?query=tuning&apropos=0&sektion=0&manpath=FreeBSD+8.0-RELEASE&format=html

greetings and a merry chrismas

michael


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