On Thu, Feb 06, 2020 at 10:48:16AM +0800, Baoquan He wrote: >On 02/06/20 at 02:26am, Wei Yang wrote: >> On Thu, Feb 06, 2020 at 08:37:36AM +0800, Baoquan He wrote: >> >On 02/06/20 at 08:13am, Baoquan He wrote: >> >> On 02/06/20 at 07:50am, Wei Yang wrote: >> >> > On Thu, Feb 06, 2020 at 07:19:45AM +0800, Wei Yang wrote: >> >> > >On Wed, Feb 05, 2020 at 02:52:51PM +0100, David Hildenbrand wrote: >> >> > >>Let's use a calculation that's easier to understand and calculates the >> >> > >>same result. Reusing existing macros makes this look nicer. >> >> > >> >> >> > >>We always want to have the number of pages (> 0) to the next section >> >> > >>boundary, starting from the current pfn. >> >> > >> >> >> > >>Suggested-by: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> >> >> > >>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> >> > >>Cc: Michal Hocko <mhocko@xxxxxxxxxx> >> >> > >>Cc: Oscar Salvador <osalvador@xxxxxxx> >> >> > >>Cc: Baoquan He <bhe@xxxxxxxxxx> >> >> > >>Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> >> >> > >>Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> >> >> > > >> >> > >Reviewed-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> >> >> > > >> >> > >BTW, I got one question about hotplug size requirement. >> >> > > >> >> > >I thought the hotplug range should be section size aligned, while taking a >> >> > >look into current code function check_hotplug_memory_range() guard the range. >> >> >> >> A good question. The current code should be block size aligned. I >> >> remember in some places we assume each block comprise all the sections. >> >> Can't imagine one or some of them are half section filled. >> > >> >I could be wrong, half filled block may not cause problem. >> > >> >> David must be angry about our flooding the mail list :-) > >Believe he won't, :-) If you like, we can talk off line. > >> >> Check the code again, there are two memory range check: >> >> * check_hotplug_memory_range(), block/section aligned >> * check_pfn_span(), subsection aligned >> >> The second check, check_pfn_span() in __add_pages(), enable the capability to >> add a memory range with subsection size. >> >> This means hotplug still keeps section alignment. > >memremap_pages() also call add_pages(), it doesn't have the >check_hotplug_memory_range() invocation. check_pfn_span() is made for >it specifically. > If my understanding is correct, memremap_pages() is used to add some dev memory to system. This is the use case which Dan want to enable for sub-section. Since memremap_pages() is not called in mem-hotplug path, this doesn't affect the hotplug range alignment. >> >> BTW, __add_pages() share the same logic as __remove_pages(). Why not change it >> too? Do I miss something or I don't have the latest source code? > >Good question, and I think it need. Just David is refactoring/cleaning >up the remove_pages() code path, this is found out by Segher from patch >reviewing. Ah, we may need a following cleanup :-) -- Wei Yang Help you, Help me
