Date: Thu, 9 Jul 1998 19:10:13 +0100 From: "Alton, Matthew" <Matthew.Alton@anheuser-busch.com> To: "'FreeBSD-fs@FreeBSD.ORG'" <FreeBSD-fs@FreeBSD.ORG>, "'Hackers@FreeBSD.ORG'" <Hackers@FreeBSD.ORG> Subject: lfs b_blkno diddling Message-ID: <31B3F0BF1C40D11192A700805FD48BF901776608@STLABCEXG011>
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I'm having some difficulty determining where the physical disk block
allocation algorithm is located. Does the lfs code (or ufs for that
matter) just use the vnodes provided by the vm system without
regard to the placement on disk (i.e. the value of (buf)->b_blkno) or
does it somehow control these things. I thought that the ffs im-
provements from 4.3BSD involved strategic physical locality of data
placement on disk and assumed that this was implemented in the
ffs code. I can see where doing a big nasty write to disk beats doing
a lot of little writes in lfs - I also assumed that lfs writes tried to
en-
force contiguity if possible, I just can't see where. The word "strat-
egy" crops up all over the place in the code. I'll look into that.
The section 9 man pages are really sparse. I'll fix the VOP_* ones
when I get this all sorted out :-)
Matthew Alton
Computer Services - UNIX Systems Administration
(314)632-6644 matthew.alton@anheuser-busch.com
alton@plantnet.com
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