Re: 2.6.11-rc1-mm1

[Karim Yaghmour]

Karim Yaghmour wrote:
> This is not good for any client that doesn't know beforehand the exact
> size of their data units, as in the case of LTT. If LTT has to use this
> code that means we are going to loose performance because we will need to
> fill an intermediate data structure which will only be used for relay_write().
> Instead of zero-copy, we would have an extra unnecessary copy. There has
> got to be a way for clients to directly reserve and write as they wish.
> Even Zach Brown recognized this in his tracepipe proposal, here's from
> his patch:
> + * 	- let caller reserve space and get a pointer into buf

Also, if the reserve is exported, then a client that chooses so, can
do something like:

	local_irq_save();
	relay_reserve();
	write(); write(); write(); ...
	local_irq_restore();

And therefore enforce in-order events is he so chooses.

Karim
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