On 29.01.21 12:46, Oscar Salvador wrote:

On Fri, Jan 29, 2021 at 12:34:51PM +0100, David Hildenbrand wrote:

quoted

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@linux-foundation.org>
Cc: Thomas Gleixner <redacted>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <redacted>
Cc: David Rientjes <rientjes@google.com>
Cc: linux-api@vger.kernel.org
Signed-off-by: David Hildenbrand <redacted>

Looks good to me, I guess it is better to print it unconditionally
so the layout does not change.

Reviewed-by: Oscar Salvador <osalvador@suse.de>

Thanks for the fast review!


-- 
Thanks,

David / dhildenb