Signed-off-by: Colin McCabe <colin.mccabe@xxxxxxxxxxxxx> --- doc/dev/logs.rst | 27 +++++++++++++++++++++++++++ 1 files changed, 27 insertions(+), 0 deletions(-) diff --git a/doc/dev/logs.rst b/doc/dev/logs.rst index f4bef84..9532763 100644 --- a/doc/dev/logs.rst +++ b/doc/dev/logs.rst @@ -29,3 +29,30 @@ the best performance. Sometimes, enabling logging can hide race conditions and other bugs by changing the timing of events. Keep this in mind when debugging. + +============ + Performance Counters +============ + +Ceph daemons use performance counters to track key statistics like number of +inodes pinned. Performance counters are essentially sets of integers and floats +which can be set, incremented, and read using the PerfCounters api. + +A PerfCounters object is usually associated with a single subsystem. It +contains multiple counters. This object is thread-safe because it is protected +by an internal mutex. You can create multiple PerfCounters objects. + +Currently, three types of performance counters are supported: u64 counters, +float counters, and long-run floating-point average counters. These are created +by PerfCountersBuilder::add_u64, PerfCountersBuilder::add_fl, and +PerfCountersBuilder::add_fl_avg, respectively. u64 and float counters simply +provide a single value which can be updated, incremented, and read atomically. +floating-pointer average counters provide two values: the current total, and +the number of times the total has been changed. This is intended to provide a +long-run average value. + +Performance counter information can be read in JSON format from the +administrative socket (admin_sock). This is implemented as a UNIX domain +socket. The Ceph peformance counter plugin for collectd shows an example of how +to access this information. Another example can be found in the unit tests for +the administrative sockets. -- 1.7.2.5 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
