To communicate with the target, Streamline requires a daemon, called gatord, to be installed and running on the target. gatord must be running before you can capture trace data.
gatord reads and processes data from applications that are running on the target. When running a headless capture, it then creates a directory, whose name ends in .apc, containing the capture data.
gatord uses the perf API to collect performance information. You can run gatord on a device with or without root permissions. Running gatord on a device with root permissions supports system-wide data collection, including profiling all applications and the kernel. When run as non-root user, gatord is limited to capturing processes that you have permission to profile. These processes are usually running as the same user.
Note
System-wide data collection using non-root gatord falls back to /proc polling, which is deprecated. To perform system-wide data collection, use root gatord.
gatord has some restrictions, for example:
It polls the following Linux counters every 100ms, instead of every 1ms or when they change because files in the /proc or /sys filesystem are read:
Memory
Disk I/O
Network
This rate is fixed and overrides the sample rate that is specified in the Capture Settings dialog box.
When using gatord, the Memory: Used counter does not contain per-process information. As a result, memory statistics are not available in Processes mode.
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