Maximum Direct-IO size on x86 platform

["Faerstain, Bert" <Bert.Faerstain@xxxxxxxxxx>]

Does anyone know if I can increase the Direct-IO size on an xfs 
filesystem running x86?  I'm getting 256K (262144) as the maxsize for 
DIO.  I want at least  6 or 7 MB.  Is this tied in some way to the 4K 
pagesize on x86? this would still seem too small.  Would looking into 
hugepage kernel params help me somehow?  what parameter can i change to 
increase the DIO maxsize?
I have a 2TB + filesystem mounted on a dual Xeon 3Ghz machine, running 
RH 2.6.6-1.435smp
Here's my xfs_info:

        [root@pastis etc]# mkfs.xfs /dev/md0
	meta-data=/dev/md0               isize=256    agcount=32, 
agsize=19789888 blks
                        =                       sectsz=512
        data  =                       bsize=4096   blocks=633276416, imaxpct=25
         		=                       sunit=64     swidth=128 blks, 
unwritten=1
                                         naming   =version 2              
bsize=4096
	log    =         internal log           bsize=4096   blocks=32768, 
version=1
                        =                       sectsz=512   sunit=0 blks
        realtime = none                   extsz=524288 blocks=0, rtextents=0

And here's the DirectIO info I get back from our DIO test app:
                ATTEMPTING TO USE DIRECT I/O
                USING DIRECT I/O
                MAXSIZE = 262144       MINSIZE = 512    ALIGN SIZE = 512
                [root@pastis]#