On Sun, Jan 28, 2001 at 12:42:35AM -0800, Sam Trenholme wrote:
>
> [Chris: We're discussing your presentation on the Qmail list]
>
> On Sat, 27 Jan 2001, Steve Fulton wrote:
>
> > http://www.users.qwest.net/~presentations/cmikk/
>
> I notice that Chris Mikkelson and the people at qwest.net use multiple
> qmail-sends on multiple queues, with a note that qmail-send is the big
> bottleneck. I wonder if they are using the big concurrency patch.
That might not be their issue. With high traffic, qmail-send spends so
much time handling todo/ that is doesn't even consider actually
delivering anything.
> Once the big concurrency patch is installed, it is trivial to get a
> concurrency of 500. The 500 number is based on Linux's limits--I would
> not be surprised if FreeBSD has far bigger limits.
We use 1024 for both local and remote. This is because we are afraid
to run out of memory because of all the processes if we allow even
more :)
They have a very good point on the page 'Getting bigger: High-capacity
forwarding', btw. I ran into the same problem, that qmail requires
double delivery for simple forwards. I 'fixed' this by turning as many
forwards as possible (all were from virtual domains to the local
domain) into a virtualdomains-entry and a users-assign entry. Works
wonderfully, and increases performance by over 100%.
Every forward means another todo/ entry, which means qmail-send will
stop delivering for a moment. That sucks for performance.
Greetz, Peter.
