Date: Wed, 21 Mar 2001 11:07:38 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Alfred Perlstein <bright@wintelcom.net> Cc: "Michael C . Wu" <keichii@iteration.net>, Rik van Riel <riel@conectiva.com.br>, Peter Wemm <peter@netplex.com.au>, izero@ms26.hinet.net, cross@math.psu.edu, grog@FreeBSD.ORG, fs@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: tuning a VERY heavily (30.0) loaded s cerver Message-ID: <200103211907.f2LJ7cp17933@earth.backplane.com> References: <200103211114.f2LBE0h57371@mobile.wemm.org> <Pine.LNX.4.21.0103211328310.9056-100000@imladris.rielhome.conectiva> <20010321120620.A932@peorth.iteration.net> <200103211817.f2LIHR416007@earth.backplane.com> <20010321102836.N12319@fw.wintelcom.net>
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:Hey, talking about large amounts of swap, did you know that:
: 4.2-STABLE FreeBSD 4.2-STABLE #1: Sat Feb 10 01:26:41 PST 2001
:has a max swap limit that's possibly 'low':
:
: b: 15912412 0 swap # (Cyl. 0 - 990*)
: c: 17912412 0 unused 0 0 # (Cyl. 0 - 1114*)
:
:If I made b == c, then i couldn't swapon it.
:
:Don't ask why I have that much swap, I just needed a bunch on a dedicated
:disk. :)
:
:--
:-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
You would have to reconfigure your kernel to reduce NSWAP from 4 to
either 2 or 1.
Bitmap overhead for swap is 2 bits per page (4K) of swap.
There is a maximum of 2G / 16 / NSWAPDEV blocks (512 byte chunks) of swap.
If NSWAPDEV is 4, this comes to:
2G/16/4x512 = 17GB.
So you would be able to create approximately four 17GB swap partitions.
If you reduce NSWAP to 2 you would be able to create approximately
two 34GB swap partitions. If you reduce NSWAP to 1 you would be able
to create approximately one 68GB swap partition.
-Matt
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