Re: Suggestion for file type detection approach

[Arvind Narayanan <arvindn meenakshi cs iitm ernet in>]

On Sun, Jan 04, 2004 at 10:30:47AM -0500, Jeffrey Stedfast wrote:
> 
> just because the bulk of the time spent will be in i/o, does not mean
> that profiling will be useless.
> 
> anyways, just out of curiosity, I timed 'ls -l' and 'file' in /usr/bin
> and here are the results I get:
I tried this too. You're getting such quick times because the disk 
blocks are cached already. It would have been very slow the first time
you tried it. Reboot and try file again if you like.

This is what I get:

$ time file /usr/bin/* > /dev/null  # first time
 
real    0m16.017s
user    0m0.310s
sys     0m0.480s

$ time file /usr/bin/* > /dev/null
 
real    0m0.455s
user    0m0.290s
sys     0m0.160s

$ time file /usr/bin/* > /dev/null
 
real    0m0.450s
user    0m0.300s
sys     0m0.150s

> 
> `time /bin/ls -l /usr/bin`
> real    0m2.783s
> user    0m0.060s
> sys     0m0.010s
> 
> `time file /usr/bin/*`
> real    0m2.788s
> user    0m0.060s
> sys     0m0.120s
> 
> looks to me like "sniffing will suck performance-wise" is a hunk of
> crap, at least assuming file-type sniffing is done efficiently.
But you can't do it efficiently unless you can magically predict
which directory the user is going to click on next. And you can't
pre-cache the entire disk, can you?

Arvind
-- 
Its all GNU to me