It's a classic mistake to think that this means that direct drievr access
is faster.
The thing is, that raw IO not only means avoiding the filesystem overhead,
or _also_ means that the kernel no longer has any control over the
requests. And that in turn means that suddenly the driver has to take
cases into account that could never happen before.
Basically, raw disk IO is _not_ necessarily noticeably faster at all. The
filesystem layer is fairly lightweight and optimized.
The only argument for raw disk IO is the caching policy issue, and I very
strongly agre with Ingo that we should consider it as such, and not get
dragged into the rathole of thinking that raw devices are somehow worth it
for some other reason.
Linus
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