On Mon 08-02-21 22:38:03, David Hildenbrand wrote: > > > Am 08.02.2021 um 22:13 schrieb Mike Rapoport <rppt@xxxxxxxxxx>: > > > > On Mon, Feb 08, 2021 at 10:27:18AM +0100, David Hildenbrand wrote: > >> On 08.02.21 09:49, Mike Rapoport wrote: > >> > >> Some questions (and request to document the answers) as we now allow to have > >> unmovable allocations all over the place and I don't see a single comment > >> regarding that in the cover letter: > >> > >> 1. How will the issue of plenty of unmovable allocations for user space be > >> tackled in the future? > >> > >> 2. How has this issue been documented? E.g., interaction with ZONE_MOVABLE > >> and CMA, alloc_conig_range()/alloc_contig_pages?. > > > > Secretmem sets the mappings gfp mask to GFP_HIGHUSER, so it does not > > allocate movable pages at the first place. > > That is not the point. Secretmem cannot go on CMA / ZONE_MOVABLE > memory and behaves like long-term pinnings in that sense. This is a > real issue when using a lot of sectremem. A lot of unevictable memory is a concern regardless of CMA/ZONE_MOVABLE. As I've said it is quite easy to land at the similar situation even with tmpfs/MAP_ANON|MAP_SHARED on swapless system. Neither of the two is really uncommon. It would be even worse that those would be allowed to consume both CMA/ZONE_MOVABLE. One has to be very careful when relying on CMA or movable zones. This is definitely worth a comment in the kernel command line parameter documentation. But this is not a new problem. -- Michal Hocko SUSE Labs
