On Tue, Feb 07, 2017 at 04:41:21PM +0100, Michal Hocko wrote: >On Tue 07-02-17 23:32:47, Wei Yang wrote: >> On Tue, Feb 07, 2017 at 10:45:57AM +0100, Michal Hocko wrote: >[...] >> >Is there any reason why for_each_mem_pfn_range cannot be changed to >> >honor the given start/end pfns instead? I can imagine that a small zone >> >would see a similar pointless iterations... >> > >> >> Hmm... No special reason, just not thought about this implementation. And >> actually I just do the similar thing as in zone_spanned_pages_in_node(), in >> which also return 0 when there is no overlap. >> >> BTW, I don't get your point. You wish to put the check in >> for_each_mem_pfn_range() definition? > >My point was that you are handling one special case (an empty zone) but >the underlying problem is that __absent_pages_in_range might be wasting >cycles iterating over memblocks that are way outside of the given pfn >range. At least this is my understanding. If you fix that you do not >need the special case, right? >-- >Michal Hocko >SUSE Labs > Not really, sorry, this area is full of awkward and subtle code when new > changes build on top of previous awkwardness/surprises. Any cleanup > would be really appreciated. That is the reason I didn't like the > initial check all that much. Looks my fetchmail failed to get your last reply. So I copied it here. Yes, the change here looks not that nice, while currently this is what I can't come up with. Thanks for your review :-) -- Wei Yang Help you, Help me
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