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Date: Tue, 9 Jan 1996 22:08:17 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199601091108.WAA17097@godzilla.zeta.org.au>
To: graichen@omega.physik.fu-berlin.de, peter@freefall.freebsd.org
Subject: Re: cvs commit: src/sys/i386/conf Makefile.i386
Cc: CVS-committers@freefall.freebsd.org, cvs-sys@freefall.freebsd.org
Sender: owner-cvs-sys@FreeBSD.ORG
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>>   Modified:    sys/i386/conf  Makefile.i386
>>   Log:
>>   Also move /var/db/kvm_kernel.db to /var/db/kvm_kernel.old.db IF we change
>>   sysctl kern.bootfile - since libkvm expects it there.
>> ...
>just one related question: why is dev.db in /var/run and not in /var/db ?

Because it is a temporary file associated with the current kernel.
kvm_kernel.db was also in /var/run in FreeBSD-1.1, but the 4.4lite
implementation of kvm_mkdb was so slow that preserving kvm_kernel.db
across boots was worthwhile.  kvm_mkdb was speeded up by a factor of
about 5 (from 20+ seconds to 4+ seconds on my 486DX33 IDE system) on
1995/01/10 by using mmap.  The speed can be improved by an additional
factor or about 2.5 without changing the application by removing ufs's
write-through for full data blocks.  Write-through is very bad for
random writes if the same block is often rewritten.

Bruce