On Wed 28-03-18 08:39:36, Wei Yang wrote: > On Tue, Mar 27, 2018 at 12:58:21PM +0200, Michal Hocko wrote: > >On Tue 27-03-18 11:57:07, Wei Yang wrote: > >> find_min_pfn_for_node() iterate on pfn range to find the minimum pfn for a > >> node. The memblock_region in memblock_type are already ordered, which means > >> the first hit in iteration is the minimum pfn. > > > >I haven't looked at the code yet but the changelog should contain the > >motivation why it exists. It seems like this is an optimization. If so, > >what is the impact? > > > > Yep, this is a trivial optimization on searching the minimal pfn on a special > node. It would be better for audience to understand if I put some words in > change log. > > The impact of this patch is it would accelerate the searching process when > there are many memory ranges in memblock. > > For example, in the case https://lkml.org/lkml/2018/3/25/291, there are around > 30 memory ranges on node 0. The original code need to iterate all those ranges > to find the minimal pfn, while after optimization it just need once. Then show us some numbers to justify the change. -- Michal Hocko SUSE Labs
