[Mimedefang] flock vs. fcntl

[Kris Deugau]

Jason Bertoch [Electronet] wrote:
> Reading the Optimizing Do's and Don'ts found at
> http://www.mimedefang.org/kwiki/index.cgi?OptimizingMIMEDefang,
> there is one line bugging me: lock_method flock.
> 
> I googled for info on these two locking methods and am hard up to find any
> recent information on which to use on my RedHat and Fedora systems.  It appears
> that fnctl works better for NFS but is there a performance difference for local
> file systems?  Does the above suggestion apply to MD, Sendmail, or for all
> software compiled on my system?  If only MD, is that set at compile time, or in
> the filter?

I don't know of anywhere in MD itself where that can be "tuned" short of 
manually hacking the source and building your own custom version.

It's most likely intended for people running SpamAssassin;  relating to 
how it locks BerkeleyDB databases (Bayes and AWL).  flock() is faster, 
but isn't generally NFS-safe;  fcntl() is (more) NFS-safe but slower.

I don't recall offhand how those calls in Perl actually relate to the 
underlying C library and/or kernel syscalls.  IIRC it varies somewhat 
depending on the OS.  :/

-kgd