Re: /usr/lib vs /usr/libexec
Thomas Bushnell BSG <tb@becket.net> writes:
> Lars Wirzenius <liw@liw.iki.fi> writes:
>
>> I may be completely wrong here, but as far as I understand, ld turns
>> -lfoo into /usr/lib/libfoo.a and then uses that if it can find it. It
>> might look into some other directories as well, and it might fill in foo
>> into some other patterns than "lib%s.a", but basically that is it. It
>> does not scan the /usr/lib directory, it merely looks up a filename it
>> knows already.
>
> Right, and "open" is O(n) on just about every system. If that's not
> true on ext2, then that's good news, and I'm surprised.
>
>> With modern filesystems, the kernel also does not need to read through
>> the entires /usr/lib directory listing: modern filesystems user B-trees
>> or other ways to speed up filename lookups. O(log n), that is, or even
>> approximately O(1) if a good hash is used.
>
> Actually, even systems as old as ITS used better than O(n)
> directories. It's Unix that has historically stunk. It's not a
> modern/old thing, it's a Just Do It thing.
>
> Which Linux filesystems have better than O(n) performance on open?
>
> Thomas
Which doesn't? Minix maybe. Even ext2/3 has hashes for dir if you
format it that way.
MfG
Goswin
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