Re: O_DIRECT question

[Bill Davidsen]

Denis Vlasenko wrote:
> On Thursday 25 January 2007 21:45, Michael Tokarev wrote:
> > Phillip Susi wrote:
> > > Denis Vlasenko wrote:
> > > > You mean "You can use aio_write" ?
> > > Exactly.  You generally don't use O_DIRECT without aio.  Combining the
> > > two is what gives the big win.
> > Well, it's not only aio.  Multithreaded I/O also helps alot -- all this,
> > say, to utilize a raid array with many spindles.
> >
> > But even single-threaded I/O but in large quantities benefits from O_DIRECT
> > significantly, and I pointed this out before.
>
> Which shouldn't be true. There is no fundamental reason why
> ordinary writes should be slower than O_DIRECT.
Other than the copy to buffer taking CPU and memory resources.

--
Bill Davidsen <davidsen@xxxxxxx>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

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