Re: O_DIRECT question

[Denis Vlasenko]

On Thursday 11 January 2007 18:13, Michael Tokarev wrote:
> example, which isn't quite possible now from userspace.  But as long as
> O_DIRECT actually writes data before returning from write() call (as it
> seems to be the case at least with a normal filesystem on a real block
> device - I don't touch corner cases like nfs here), it's pretty much
> THE ideal solution, at least from the application (developer) standpoint.

Why do you want to wait while 100 megs of data are being written?
You _have to_ have threaded db code in order to not waste
gobs of CPU time on UP + even with that you eat context switch
penalty anyway.

I hope you agree that threaded code is not ideal performance-wise
- async IO is better. O_DIRECT is strictly sync IO.
--
vda
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