NOW: o_direct -- WAS: Re: WARNING in xfs_lwr.c, xfs_write()

[Stan Hoeppner]

Christoph Hellwig put forth on 5/27/2010 6:47 AM:
> O_DIRECT is not a Posix standard and not very portable.  It originated
> on IRIX, and Linux inherited it during the 2.4 kernel series days.
> These days FreeBSD/NetBSD and AIX support it as well, but for example
> Solaris, HP-UX and OpenBSD don't, nevermind Windows or Mac OS.
> 
> I have no idea why the MTAs don't want to use it - it's generally easier
> to use then memory mapped I/O, and has much more deterministic
> performance.

Thanks for the background Christoph.  I can now see why Postfix and Dovecot in
particular don't use O_DIRECT: portability.  They both are developed to run on
every Unix/like OS you mention above, half of which don't offer O_DIRECT.  I'm
guessing the same may likely be true for the other SMTP MTAs and IMAP servers.

-- 
Stan