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diff --git a/src/ceph/doc/dev/logs.rst b/src/ceph/doc/dev/logs.rst deleted file mode 100644 index 7fda64f..0000000 --- a/src/ceph/doc/dev/logs.rst +++ /dev/null @@ -1,57 +0,0 @@ -============ - Debug logs -============ - -The main debugging tool for Ceph is the dout and derr logging functions. -Collectively, these are referred to as "dout logging." - -Dout has several log faculties, which can be set at various log -levels using the configuration management system. So it is possible to enable -debugging just for the messenger, by setting debug_ms to 10, for example. - -Dout is implemented mainly in common/DoutStreambuf.cc - -The dout macro avoids even generating log messages which are not going to be -used, by enclosing them in an "if" statement. What this means is that if you -have the debug level set at 0, and you run this code:: - - dout(20) << "myfoo() = " << myfoo() << dendl; - - -myfoo() will not be called here. - -Unfortunately, the performance of debug logging is relatively low. This is -because there is a single, process-wide mutex which every debug output -statement takes, and every debug output statement leads to a write() system -call or a call to syslog(). There is also a computational overhead to using C++ -streams to consider. So you will need to be parsimonious in your logging to get -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 performance 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. |