Re: flush cache range proposal (was Re: ide errors in 7-rc1-mm1 and later)

[Jens Axboe]

On Fri, Jun 11 2004, Jeff Garzik wrote:
> Unfortunately, that's not the answer drive guys want to hear, because 
> FUA limits the optimization potential from previous ATA.  ;-)  Maybe 
> drive performance is high enough these days that queued-FUA as a 
> standard mode of operation is tolerable...

Data integrity doesn't come for free. Take a pick :-)

> >If the drive receives a queued barrier write (NCQ or Legacy), it will
> >finish processing all previously-received queued commands and post
> >good status for them, then it will process the barrier operation, post
> >status for that barrier operation, then it will continue processing
> >queued commands in the order received.
> 
> If queued-FUA is out of the question, this seems quite reasonable.  It 
> appears to achieve the commit-block semantics described for barrier 
> operation, AFAICS.

Actually from Linux's point of view, drive may reorder previously
committed requests - just not around the barrier.

-- 
Jens Axboe

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