Separating Kernel And User-Space Profiles - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

opcontrol --event=<event-name>:<sample-rate>
Replace <sample-rate> with the number of events to wait before sampling again. The smaller the
count, the more frequent the samples. For events that do not happen frequently, a lower count may be
needed to capture the event instances.
Caution
Be extremely careful when setting sampling rates. Sampling too frequently can overload
the system, causing the system to appear as if it is frozen or causing the system to
actually freeze.
39.2.2.2. Unit Masks
Some user performance monitoring events may also require unit masks to further define the event.
Unit masks for each event are listed with the ophelp command. The values for each unit mask are
listed in hexadecimal format. To specify more than one unit mask, the hexadecimal values must be
combined using a bitwise or operation.
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>

39.2.3. Separating Kernel and User-space Profiles

By default, kernel mode and user mode information is gathered for each event. To configure OProfile
to ignore events in kernel mode for a specific counter, execute the following command:
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>:0
Execute the following command to start profiling kernel mode for the counter again:
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>:1
To configure OProfile to ignore events in user mode for a specific counter, execute the following
command:
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>:<kernel>:0
Execute the following command to start profiling user mode for the counter again:
opcontrol --event=<event-name>:<sample-rate>:<unit-mask>:<kernel>:1
When the OProfile daemon writes the profile data to sample files, it can separate the kernel and library
profile data into separate sample files. To configure how the daemon writes to sample files, execute
the following command as root:
Separating Kernel and User-space Profiles
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