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Date:      Thu, 21 Nov 2002 12:55:15 -0800
From:      David Schultz <dschultz@uclink.Berkeley.EDU>
To:        Petri Helenius <pete@he.iki.fi>
Cc:        freebsd-questions@FreeBSD.ORG, freebsd-net@FreeBSD.ORG
Subject:   Re: panic: kmem_map too small
Message-ID:  <20021121205515.GA5716@HAL9000.homeunix.com>
In-Reply-To: <126801c2912c$5be3cec0$862a40c1@PHE>
References:  <0e3b01c28fc4$ff9a4ee0$862a40c1@PHE> <20021119152114.GA2228@HAL9000.homeunix.com> <3DDBDE2B.6050407@he.iki.fi> <20021120195919.GA679@HAL9000.homeunix.com> <11fd01c290eb$f48311e0$862a40c1@PHE> <20021121022524.GA2300@HAL9000.homeunix.com> <126801c2912c$5be3cec0$862a40c1@PHE>

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Thus spake Petri Helenius <pete@he.iki.fi>:
> > > With about 150M in use and KVA_PAGES undefined in config (default),
> > > both 4.7-STABLE and 5.0-CURRENT panic (1G installed memory).
> >
> > Yes, the default is 256, IIRC.  That corresponds to 1 GB of KVA,
> > and you have only 1 GB of physical memory to back it.  I take it
> > this is a very busy machine.  Short of getting more memory, you
> > can decrease memory utilization by the network, e.g. by decreasing
> > TCP window sizes, or you can limit memory usage by the network so
> > you don't get panics.  I forget the details here, so perhaps
> > someone else can fill them in.
> >
> The thing I´m concerned about that if with 150M kernel memory usage and
> >200M free and >300M inact memory the system panics, how much "extra"
> memory is needed to keep it running? And the swap is never touched.

Most kernel memory is not pageable, so swap probably won't help
you.  Your `kmem_map too small' error message should report to you
the size of the attempted allocation and the size of kmem_map.
If the map really isn't full, I'm not sure why you would get this
panic, unless you're somehow running into excessive fragmentation.

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