On Mon, Jan 15, 2024 at 05:34:36PM +0800, Vern Hao wrote: > From: Xin Hao <vernhao@xxxxxxxxxxx> > > With this patch, we can see the distribution of pages of different orders on > each cpu, just like below. > #cat /proc/zoneinfo > .... > cpu: 2 > total_count: 14286 > order0 : 1260 > order1 : 13 > order2 : 42 > order3 : 4 > order4 : 0 > order5 : 0 > order6 : 0 > order7 : 0 > order8 : 0 > order9 : 25 > order10: 0 > order11: 0 > order12: 0 > high: 14541 > batch: 63 > > Signed-off-by: Xin Hao <vernhao@xxxxxxxxxxx> I am not a major fan because increasing the size of a per-cpu structure for debugging purposes incurs a cost for everyone while only a tiny minority may care. There is a mild risk it would break existing parsers of that file although maybe that's not a big deal. However, the same information could be extracted by locking the pcp structures and counting the items per list. It would increase the cost of reading zoneinfo but it's unlikely the file is read at high frequency. If that was a concern, a separate proc file could be used. Finally, the same information likely can be extracted via a systemtap script, a BPF script (if it can get to the right symbols and locking, I didn't check) or via a kernel probe. Even with that information, it's not clear what meaningful action a user can take, so this is a developer-only feature really with a cost incurred for everybody. -- Mel Gorman SUSE Labs
