On Tue 10-09-19 14:23:40, Alexander Duyck wrote: [...] > We don't put any limitations on the allocator other then that it needs to > clean up the metadata on allocation, and that it cannot allocate a page > that is in the process of being reported since we pulled it from the > free_list. If the page is a "Reported" page then it decrements the > reported_pages count for the free_area and makes sure the page doesn't > exist in the "Boundary" array pointer value, if it does it moves the > "Boundary" since it is pulling the page. This is still a non-trivial limitation on the page allocation from an external code IMHO. I cannot give any explicit reason why an ordering on the free list might matter (well except for page shuffling which uses it to make physical memory pattern allocation more random) but the architecture seems hacky and dubious to be honest. It shoulds like the whole interface has been developed around a very particular and single purpose optimization. I remember that there was an attempt to report free memory that provided a callback mechanism [1], which was much less intrusive to the internals of the allocator yet it should provide a similar functionality. Did you see that approach? How does this compares to it? Or am I completely off when comparing them? [1] mostly likely not the latest version of the patchset http://lkml.kernel.org/r/1502940416-42944-5-git-send-email-wei.w.wang@xxxxxxxxx -- Michal Hocko SUSE Labs
