Messages in this thread | | | Date | Thu, 2 Oct 2014 14:50:52 +0200 | From | Peter Zijlstra <> | Subject | Re: RFC: get_user_pages_locked|unlocked to leverage VM_FAULT_RETRY |
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On Thu, Oct 02, 2014 at 02:31:17PM +0200, Andrea Arcangeli wrote: > On Wed, Oct 01, 2014 at 05:36:11PM +0200, Peter Zijlstra wrote: > > For all these and the other _fast() users, is there an actual limit to > > the nr_pages passed in? Because we used to have the 64 pages limit from > > DIO, but without that we get rather long IRQ-off latencies. > > Ok, I would tend to think this is an issue to solve in gup_fast > implementation, I wouldn't blame or modify the callers for it. > > I don't think there's anything that prevents gup_fast to enable irqs > after certain number of pages have been taken, nop; and disable the > irqs again. >
Agreed, I once upon a time had a patch set converting the 2 (x86 and powerpc) gup_fast implementations at the time, but somehow that never got anywhere.
Just saying we should probably do that before we add callers with unlimited nr_pages.
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