less aggressive contigmalloc ?

[Luigi Rizzo]

I am trying to make netmap adapt the amount of memory it allocates
to what is available. At its core, it uses contigmalloc() with
small chunks (even down to 1 page) to fetch memory.

Problem is, i notice that before failing, contigmalloc()
tries to swap out some processes (effectively killing them
because i have no swap configured in my picobsd image).
This happens with both M_WAITOK and M_NOWAIT, the difference
is only in the number of retries it does -- see e.g.

	sys/vm/vm_kern.c :: kmem_alloc_contig()

where it retries once for M_NOWAIT and 3 times for M_WAITOK.

I wonder if there is a way to make contigmalloc less aggressive
and fail without killing those innocent processes ?

cheers
luigi