• Steven Rostedt's avatar
    tracing: export stats of ring buffers to userspace · c8d77183
    Steven Rostedt authored
    This patch adds stats to the ftrace ring buffers:
     # cat /debugfs/tracing/per_cpu/cpu0/stats
     entries: 42360
     overrun: 30509326
     commit overrun: 0
     nmi dropped: 0
    Where entries are the total number of data entries in the buffer.
    overrun is the number of entries not consumed and were overwritten by
    the writer.
    commit overrun is the number of entries dropped due to nested writers
    wrapping the buffer before the initial writer finished the commit.
    nmi dropped is the number of entries dropped due to the ring buffer
    lock being held when an nmi was going to write to the ring buffer.
    Note, this field will be meaningless and will go away when the ring
    buffer becomes lockless.
    [ Impact: let userspace know what is happening in the ring buffers ]
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>