Messages in this thread | | | Date | Sat, 24 Feb 2007 13:42:06 +0100 | From | Jens Axboe <> | Subject | Re: REQ_HARDBARRIER and REQ_SOFTBARRIER |
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On Sat, Feb 24 2007, V P wrote: > Hi, > > I'm trying to modify the ordering of I/O requests in Linux kernel, and > came across the barrier flags REQ_HARDBARRIER and REQ_SOFTBARRIER. > > One thing I noticed (which might be wrong) is that all the requests > have both these flags set. What is the significance of these flags? Is
Uhm? That's definitely not true.
> it a must for a request to have this? Can I reorder two requests with > these flags set? How is SOFTBARRIER different from HARDBARRIER?
Both imply a reordering barrier in the io scheduler, and the hard barrier further implies a barrier at the drive/driver side. So you may not reorder across a barrier.
-- Jens Axboe
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