Re: O_DIRECT in freebsd

Christopher Kings-Lynne <chriskl@familyhealth.com.au> writes:

> FreeBSD 4.9 was released today.  In the release notes was:
> 
> 2.2.6 File Systems
> 
> A new DIRECTIO kernel option enables support for read operations that
> bypass the buffer cache and put data directly into a userland
> buffer. This feature requires that the O_DIRECT flag is set on the
> file descriptor and that both the offset and length for the read
> operation are multiples of the physical media sector size.
> 
> Is that of any use?

Linux and Solaris have had this for a while.  I'm pretty sure it's
been discussed before--search the archives.  I think the consensus
was that it might be useful for WAL writes, but would be a fair amount
of work and would introduce portability issues...

-Doug