alloc_contig_range is the core worker function for CMA allocation
so it has every information to be able to understand allocation
latency. For example, how many pages are migrated, how many time
unmap was needed to migrate pages, how many times it encountered
errors by some reasons.
This patch adds such statistics in the alloc_contig_range and
return it to user so user can use those information to analyize
latency. The cma_alloc is first user for the statistics, which
export the statistics as new trace event(i.e., cma_alloc_info).
It was really usefuli to optimize cma allocation work.
Bug: 192475091
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I7be43cc89d11078e2a324d2d06aada6d8e9e1cc9
Signed-off-by: Richard Chang <richardycc@google.com>
(cherry picked from commit 675e504598)
a7f55c5c73