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Re: Proposal: B_ARRIER (addresses wapbl performance?)
On Tue, Dec 09, 2008 at 12:56:27PM -0800, Jason Thorpe wrote:
> On Dec 9, 2008, at 12:23 PM, Manuel Bouyer wrote:
>> Sure. And you don't care much about command completion either, as
>> long as the write to disk happen in order.
> And the only way to ensure that is using FUA (or explicit cache
But to enforce that using FUA, you have to set FUA on *every* write.
And I do not understand the "only way" in your remark above. Under
the constraint "if WCE is set in the cache control page" I agree that
it is correct. But as far as I can tell, if WCE is *not* set, it is
not in fact the case that using FUA is the "only way" to ensure that
writes are committed to stable storage in order -- because the tag
ordering rules require ordered tags to complete, um, well, in-order,
and if WCE is not set, commands are not supposed to complete until
the bits are on oxide.
I am sure I am misunderstanding something. What?
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