Direct Server Return and FreeBSD 5

[John David Duncan]

There's a load balancing configuration known as direct server return
(DSR), in which packets pass from the client through the load balancer to
the server, but then the replies from the server go directly to the client
(bypassing the load balancer).  The way this works is that the load
balancer sends the server an IP packet with the virtual IP address as its
destination addr, inside an ethernet frame whose destination is the real
MAC addr of the server. The server replies with a normal packet using the
VIP as the source addr.

The usual way to configure a BSD box to work this way is to bring up the
VIP as an alias on the loopback address, like this:
   ifconfig lo0 add 1.2.3.4 netmask 0xff00

As far as I can tell from my testing, this trick just doesn't work on my
box running -CURRENT.  In tcpdump I see packets coming in but none
going out.

Does anybody know why, or what I would have to do to change the behavior?

- JD


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Re: Performance problems with 5.0-RELEASE

[John David Duncan]

> H and < should only make a difference if you are low on memory. R is on
> by default in 5.0 anyway, due to A and J being on by default.  Setting
> malloc.conf to "aj" makes it work like it does in 4.*.

Here are some benchmarks to illustrate that, using ubench (from
/usr/ports/benchmarks) on a dual xeon machine.  Ubench MEM is
about 25% higher with "aj" than with the default.


4.7 5.0 with no5.0 with "aj"
malloc.conf
  ---
Ubench CPU:   171031 159942   162281
Ubench MEM:69884  6010474198


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