On Thu 09-02-17 21:59:29, Wei Yang wrote: > 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. THen I will suggest dropping this patch from the mmotm tree because it doesn't sound like a big improvement and I would encourage you or anybody else to take a deeper look and unclutter this area to be more readable and better maintainable. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
