less aggressive contigmalloc ?

From: Luigi Rizzo <rizzo_at_iet.unipi.it>
Date: Wed, 22 Aug 2012 14:01:05 +0200
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
Received on Wed Aug 22 2012 - 09:41:59 UTC

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