On Thu, Nov 15, 2018 at 01:37:35PM -0800, Andrew Morton wrote: >On Thu, 15 Nov 2018 07:50:40 +0800 Wei Yang <richard.weiyang@xxxxxxxxx> wrote: > >> For one zone, there are three digits to describe its space range: >> >> spanned_pages >> present_pages >> managed_pages >> >> The detailed meaning is written in include/linux/mmzone.h. This patch >> concerns about the last two. >> >> present_pages is physical pages existing within the zone >> managed_pages is present pages managed by the buddy system >> >> >From the definition, managed_pages is a more strict condition than >> present_pages. >> >> There are two functions using zone's present_pages as a boundary: >> >> populated_zone() >> for_each_populated_zone() >> >> By going through the kernel tree, most of their users are willing to >> access pages managed by the buddy system, which means it is more exact >> to check zone's managed_pages for a validation. >> >> This patch replaces those checks on present_pages to managed_pages by: >> >> * change for_each_populated_zone() to for_each_managed_zone() >> * convert for_each_populated_zone() to for_each_zone() and check >> populated_zone() where is necessary >> * change populated_zone() to managed_zone() at proper places >> >> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> >> >> --- >> >> Michal, after last mail, I did one more thing to replace >> populated_zone() with managed_zone() at proper places. >> >> One thing I am not sure is those places in mm/compaction.c. I have >> chaged them. If not, please let me know. >> >> BTW, I did a boot up test with the patched kernel and looks smooth. > >Seems sensible, but a bit scary. A basic boot test is unlikely to >expose subtle gremlins. > Agree. >Worse, the situations in which managed_zone() != populated_zone() are >rare(?), so it will take a long time for problems to be discovered, I >expect. Hmm... I created a virtual machine with 4 nodes, which has total 6 populated zones. All of them are different. This is a little bit out of my expactation. > >I'll toss it in there for now, let's see who breaks :( Thanks. -- Wei Yang Help you, Help me
