On Thu, Jan 05, 2017 at 08:01:02PM -0500, Steven Rostedt wrote: > Commit 682a3385e773 "mm, page_alloc: inline the fast path of the > zonelist iterator" changed how next_zones_zonelist() is called, by > adding a static inline function to do the fast path. This function adds: > > if (likely(!nodes && zonelist_zone_idx(z) <= highest_zoneidx)) > return z; > return __next_zones_zonelist(z, highest_zoneidx, nodes); > > Where __next_zones_zonelist() is only called when nodes is not NULL or > zonelist_zone_idx(z) is less than highest_zoneidx. > > The original next_zone_zonelist() was converted to > __next_zones_zonelist() but it still maintained: > > if (likely(nodes == NULL)) > > Which is now actually a very unlikely, as it is only called with nodes > equal to NULL when zonelist_zone_idx(z) is greater than highest_zoneidx. > > Before this commit, this if had this statistic: > > correct incorrect % Function File Line > ------- --------- - -------- ---- ---- > 837895 446078 34 next_zones_zonelist mmzone.c 63 > > After this commit, it has: > > correct incorrect % Function File Line > ------- --------- - -------- ---- ---- > 10 173840 99 __next_zones_zonelist mmzone.c 63 > > Thus, the if statement is now much more unlikely than it ever was as a > likely. > > Signed-off-by: Steven Rostedt (VMware) <[email protected]>
Well spotted; Acked-by: Mel Gorman <[email protected]> -- Mel Gorman SUSE Labs
