Date: Sat, 13 Jan 2001 14:05:51 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Bruce Burden <brucegb@realtime.net> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: /swap too large? What?? Message-ID: <200101132205.f0DM5pJ35749@earth.backplane.com> References: <20010113002643.A33278@tigerfish2.my.domain> <200101131927.f0DJRSS34276@earth.backplane.com> <20010113150956.B37497@tigerfish2.my.domain>
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: Hi Matt,
:>
:> The only thing that can cause this is if you have configured an
:> absurdly large NSWAPDEV.
:>
: Well, I had NSWAPDEV set for 20 (why? I don't know!) but
: according to my calculations, that should still allow a 3.4GB
: swap, or 2x what I have.
:
: I have dropped things back to NSWAPDEV=3, and see if that
: does anything.
:
: Bruce
That will fix it.
Generally speaking the amount of bitmap space the kernel must allocate
scales with (largest swap partition) * NSWAPDEV. An NSWAPDEV of 4
(the default) is reasonable for most swap configurations. But if you
have NSWAPDEV of 20 and are only using one or two swap devices (and one
of them is a gig), then the kernel winds up having to reserve bitmap
space for (1 gig) x 20 blocks, which wastes a huge amount of kernel
memory unnecessarily.
This is all in the name of making interleaved swap work.
-Matt
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