• Mel Gorman's avatar
    sched: add tracepoints related to NUMA task migration · 286549dc
    Mel Gorman authored
    This patch adds three tracepoints
     o trace_sched_move_numa	when a task is moved to a node
     o trace_sched_swap_numa	when a task is swapped with another task
     o trace_sched_stick_numa	when a numa-related migration fails
    
    The tracepoints allow the NUMA scheduler activity to be monitored and the
    following high-level metrics can be calculated
    
     o NUMA migrated stuck	 nr trace_sched_stick_numa
     o NUMA migrated idle	 nr trace_sched_move_numa
     o NUMA migrated swapped nr trace_sched_swap_numa
     o NUMA local swapped	 trace_sched_swap_numa src_nid == dst_nid (should never happen)
     o NUMA remote swapped	 trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
     o NUMA group swapped	 trace_sched_swap_numa src_ngid == dst_ngid
    			 Maybe a small number of these are acceptable
    			 but a high number would be a major surprise.
    			 It would be even worse if bounces are frequent.
     o NUMA avg task migs.	 Average number of migrations for tasks
     o NUMA stddev task mig	 Self-explanatory
     o NUMA max task migs.	 Maximum number of migrations for a single task
    
    In general the intent of the tracepoints is to help diagnose problems
    where automatic NUMA balancing appears to be doing an excessive amount
    of useless work.
    
    [akpm@linux-foundation.org: remove semicolon-after-if, repair coding-style]
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Reviewed-by: default avatarRik van Riel <riel@redhat.com>
    Cc: Alex Thorlton <athorlton@sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    286549dc
fair.c 188 KB