[Patch] Speed up /usr/lib/vdr/plugin-loader.sh by a factor of 20

[Michael Burian]

Dear VDR Maintainers,

On my Laptop: (1.8 Ghz Dualcore Centrino, 1GB RAM, SATA Harddisk, Debian 
Lenny) it takes 40+ seconds till the whole plugin handling is done.

After tracking down the issue "dpkg -S" looked highly suspicious.

To rule out any other issues that might cause the horrible performance I
booted into single user mode (init=/bin/bash) and did a

time dpkg -S /usr/bin/bashbug

which took, about 41 seconds for the first run on a fresh booted
system.

Using strace to see what's going on behind the scenes I found out that
"dpkg -S" involves reading all those little /var/lib/dpkg/info/*.list
files. (which turn out to be 2822 files / 26MB disk usage on my laptop)

bootchart also showed heavy IO during those 41 seconds

Fortunately there are less IO intensive ways to get that kind of 
information. This is where my patch comes in:


About the patch:

1. dlocate is used if available
2. dpkg is used if dlocate is not available
3. vdr package should "Suggests:" or maybe even "Depends:" on dlocate
4. Is really necessary to always perform an update-dlocatedb?(+0.6 secs)
5. Does it make sense to inform the user that dlocate is used?
(or would it make sense to recommend installing dlocate in case
  the user is experiencing slow start up behavior?)

Performance:

initial start up:
a common case, usually we aren't restarting vdr all day long

dpkg -S  41 seconds
dlocate -S 2 seconds

After the initial run dpkg might be a bit faster, likely due to the fact 
that files that are already cached in memory and no update-dlocatedb is 
performed in that case. (See 4.) Compared to the initial delays that 
difference is appears to be negligible, however.


What do you think about it?
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