This is interesting, because one real advantage
of O_DIRECT are these greased weasel fast 15-20 Mb/s
file copies, which ones makes windoze users to look
on us as on lesser beings.
I understand, though, that this approach scales
bad in the terms of multithread loads, which ones are
especially important in server environments, the place
linux initially growed from, and that is why it wasn`t
One more problem i see here, and i think it is an
*extremely* important one, that making open( ... ,
BLA_BLA_BLA | O_DIRECT) is a thing some people may
overspeculate with. I mean that implementing O_DIRECT
in cp(1), wins the prize, but in the case of, say,
find(1) it is definitely not a wise move. The problem
may be determined as "poisoning" software with this
godblessed O_DIRECT, to the state, when 70% of code
on an average machine will use it, thus *completely*
killing the advantages of buffered access, and
suddenly *bang!*: the overall performance is died.
But the worst thing, is what the process of
poisoning is completely uncontrollable: each
stupid doodie can think, that His shitful piece of Code,
is Especially Important, ant that in his case O_DIRECT
is perfectly suitable. And in the case His code is
someway performance critical, then most likely O_DIRECT
will really improve his Code benchmarks, and that is
making things really awful, leading to the hell large
crowd of pig happy dudes thinking their useless code
is life critical, and thus dooming linux.
Maybe i`m stupid, as these potential dudes, and
painting things in too dark colors, but O_DIRECT,
i think, is a dangerous thing to play with.
That is why, i think, Linus as far as i can properly
recall, wasn`t happy with it et al.
Maybe i`m missing the whole point, and thus i want to
hear what other people will tell about it.
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