Victor Duchovni:
> On Tue, Nov 23, 2010 at 07:35:49PM -0500, Wietse Venema wrote:
>
> > Victor Duchovni:
> > > On Tue, Nov 23, 2010 at 05:20:11PM -0600, Stan Hoeppner wrote:
> > >
> > > > Would you please give us the run down on why these map types (and maybe
> > > > others) shouldn't be used with proxymap due to performance reasons? You
> > > > mentioned something about this long ago but I can't seem to locate that
> > > > email in my archives. IIRC you didn't go into much technical detail as
> > > > to why the performance would be lower using proxymap.
> > >
> > > There is no point in using IPC to ask a server to read a file, when the
> > > client process can read it directly. Especially with CDB, since there
> > > is no per-client page pool adding some per-client memory overhead.
> >
> > With Stan's huge CIDR maps on a small machine, proxymap helps
> > to avoid running out of memory.
>
> CIDR maps are indeed a different kettle of fish, they are not
> "read-a-file via IPC", rather they are "do a memory lookup via IPC", and
> if the memory footprint is sufficiently high (lots Berkeley DB tables or
> huge CIDR tables), then indeed one may want to use proxymap.
>
> With "cdb" (the recommended read-only indexed table type for Postfix) direct
> access is best.
proxymap is OK for moderate traffic to expensive or otherwise
inaccessible resources. Opening a CDB map is not expensive, an
SQL database handle or memory-based map (regexp etc.) can be
expensive, and /etc/passwd can be inaccessible due to lazy opens.
proxymap is not the best solution if you need minimal latency at
all cost.
Wietse
