The KTR_ENTRIES option sets the size of the buffer of events. The size of the buffer in the currently running kernel can be found via the sysctl debug.ktr.entries. By default the buffer contains 1024 entries.
Secondly, the actual events logged while the kernel runs can be further masked via the run time event mask. The KTR_MASK option sets the default value of the run time event mask. The runtime event mask can also be set by the loader(8) via the debug.ktr.mask environment variable. It can also be examined and set after booting via the debug.ktr.mask sysctl. By default the run time mask is set to block any tracing. The definitions of the event mask bits can be found in <sys/ktr.h>.
Furthermore, there is a CPU event mask whose default value can be changed via the KTR_CPUMASK option. When two or more parameters to KTR_CPUMASK, are used, it is important they are not separated by whitespace. A CPU must have the bit corresponding to its logical id set in this bitmask for events that occur on it to be logged. This mask can be set by the loader(8) via the debug.ktr.cpumask environment variable. It can also be examined and set after booting via the debug.ktr.cpumask sysctl. By default, only CPUs specified in KTR_CPUMASK will log events. See sys/conf/NOTES for more information.
|displays or sets the file that ktr will log to. By default its value is /tmp/ktr.out. If the file name is changed while ktr is enabled it will not take effect until the next invocation.
|enables logging of ktr entries to disk if it is set to one. Setting this to 0 will terminate logging to disk and revert to logging to the normal ktr ring buffer. Data is not sent to the ring buffer while logging to disk.
|is the maximum number of entries that will be recorded to disk, or 0 for infinite. This is helpful for limiting the number of particularly high frequency entries that are recorded.
|determines the number of entries in the write buffer. This is the buffer that holds entries before they are written to disk and defaults to the value of the KTR_ENTRIES option.
|records the number of times we failed to write an entry due to overflowing the write buffer. This may happen if the frequency of the logged ktr messages outpaces the depth of the queue.
|records the number of entries that have currently been written to disk.
|October 20, 2012
|I have a natural revulsion to any operating system that shows so little planning as to have to named all of its commands after digestive noises (awk, grep, fsck, nroff).