On Fri, 29 Jan 2021, David Hildenbrand wrote: > Let's count the number of CMA pages per zone and print them in > /proc/zoneinfo. > > Having access to the total number of CMA pages per zone is helpful for > debugging purposes to know where exactly the CMA pages ended up, and to > figure out how many pages of a zone might behave differently, even after > some of these pages might already have been allocated. > > As one example, CMA pages part of a kernel zone cannot be used for > ordinary kernel allocations but instead behave more like ZONE_MOVABLE. > > For now, we are only able to get the global nr+free cma pages from > /proc/meminfo and the free cma pages per zone from /proc/zoneinfo. > > Example after this patch when booting a 6 GiB QEMU VM with > "hugetlb_cma=2G": > # cat /proc/zoneinfo | grep cma > cma 0 > nr_free_cma 0 > cma 0 > nr_free_cma 0 > cma 524288 > nr_free_cma 493016 > cma 0 > cma 0 > # cat /proc/meminfo | grep Cma > CmaTotal: 2097152 kB > CmaFree: 1972064 kB > > Note: We print even without CONFIG_CMA, just like "nr_free_cma"; this way, > one can be sure when spotting "cma 0", that there are definetly no > CMA pages located in a zone. > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx> > Cc: Mike Rapoport <rppt@xxxxxxxxxx> > Cc: Oscar Salvador <osalvador@xxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > Cc: David Rientjes <rientjes@xxxxxxxxxx> > Cc: linux-api@xxxxxxxxxxxxxxx > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
