I wondered about that as well -- could speed things
up by 30% over going through the slow linux buffers.
One thing that the 'dd' people found out though was
that if you do direct I/O, memory and your I/O really
do have to line up -- it may be that only 512 byte alignment
is necessary (or 4096 on some newer disks)...but ideally,
you look at the stat's claim for write size since the last
param in stat isn't the allocation size, but the smallest
optimal write size -- i.e. the "stripe size" if you have
a RAID...as there, you want to write whole strips at once,
otherwise you get into a read/modify/write cycle that slows
down your disk I/O with 200% overhead -- *ouch!*...
Dag Wieers wrote:
Hi,
Since a --direct-io feature was requested a few times the past decade
with little response and the actual patch is quite trivial, I patched
both v3.0.9 and master branch and included the patches here.
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