From: utzoo!decvax!wivax!dyer
Newsgroups: net.unix-wizards
Title: Re: dump/restor SLOW -- why?
Article-I.D.: wivax.4456
Posted: Sun Jan 30 19:16:44 1983
Received: Mon Jan 31 03:46:50 1983
References: pwa-b.55

At BBNCC, we were concerned about the speed of "restor" (V7), mainly because
we were in the midst of recovering from a operator-induced file-system
crash.  Full restor's were taking about 30-40 minutes, most of it in
the CPU-intensive phase BEFORE the tape starts moving.

After compiling a profiling version of restor, it turned out that a large
amount of its time was spent in two routines, copy and clearblk,
(guess what they do?).  On the C/70, by replacing them with microcode
routines having the same semantics, the time to perform a "restor" dropped
to roughly to 5-10 minutes.

It might be interesting to construct a version of "restor" for the VAX,
using an appropriately configured "asm.sed" to replace calls to copy()
and clearblk() with equvalent VAX block-move and block-copy single
instructions.

Steve Dyer
sdyer@bbn-unix
decvax!wivax!dyer
dyer.Wang-Inst@udel-relay