On Wed, Sep 11, 2019 at 01:36:19PM +0200, Michal Hocko wrote: > 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 Linus nacked that one. He thinks invoking callbacks with lots of internal mm locks is too fragile.
