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. 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. I'll toss it in there for now, let's see who breaks :(
