On Tue, Jan 11, 2011 at 12:45:02PM -0500, Tom Lane wrote: > Florian Pflug <f...@phlo.org> writes: > > On Jan11, 2011, at 18:09 , Garick Hamlin wrote: > >> My gut was that direct io would likely work right on Linux > >> and Solaris, at least. > > > Didn't we discover recently that O_DIRECT fails for ext4 on linux > > if ordered=data, or something like that? > > Quite. Blithe assertions that something like this "should work" aren't > worth the electrons they're written on.
Indeed. I wasn't making such a claim in case that wasn't clear. I believe, in fact, there is no single way that will work everywhere. This isn't needed for correctness of course, it is merely a tweak for performance as long as the 'not working case' on platform + filesystem X case degrades to something close to what would have happened if we didn't try. I expected POSIX_FADV_NOREUSE not to work on Linux, but haven't looked at it recently and not all systems are Linux so I mentioned it. This was why I thought direct io might be more realistic. I did not have a chance to test before I wrote this email so I attempted to make my uncertainty clear. I _know_ it will not work in some environments, but I thought it was worth looking at if it worked on more than one sane common setup, but I can understand if you feel differently about that. Garick > > regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
