Messages in this thread | | | Date | Thu, 10 Jan 2008 11:57:26 +0100 | From | Ingo Molnar <> | Subject | Re: CPA patchset |
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* Andi Kleen <ak@suse.de> wrote:
> > > > WBINVD isnt particular fast (takes a few msecs), but why is > > > > that a problem? Drivers dont do high-frequency ioremap-ing. > > > > It's typically only done at driver/device startup and that's > > > > it. > > > > > > Actually graphics drivers can do higher frequency allocation of WC > > > memory (with PAT) support. > > > > but that's not too smart: why dont they use WB plus cflush instead? > > Because they need to access it WC for performance.
I think you have it fundamentally backwards: the best for performance is WB + cflush. What would WC offer for performance that cflush cannot do?
also, it's irrelevant to change_page_attr() call frequency. Just map in everything from the card and use it. In graphics, if you remap anything on the fly and it's not a slowpath you've lost the performance game even before you began it.
Ingo
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