trace-cmd-snapshot - Man Page

take, reset, free, or show a Ftrace kernel snapshot

The trace-cmd(1) snapshot controls or displays the Ftrace Linux kernel snapshot feature (if the kernel supports it). This is useful to "freeze" an instance of a live trace but without stopping the trace.

 trace-cmd start -p function
 trace-cmd snapshot -s
 trace-cmd snapshot
[ dumps the content of buffer at 'trace-cmd snapshot -s' ]
 trace-cmd snapshot -s
 trace-cmd snapshot
[ dumps the new content of the buffer at the last -s operation ]

Options

-s: Take a snapshot of the currently running buffer.
-r: Clear out the buffer.
-f: Free the snapshot buffer. The buffer takes up memory inside the kernel. It is best to free it when not in use. The first -s operation will allocate it if it is not already allocated.
-c cpu: Operate on a per cpu snapshot (may not be fully supported by all kernels)
-B buf: If a buffer instance was created, then the -B option will operate on the snapshot within the buffer.