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SubjectRe: O_DIRECT question
Date
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@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot

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