The up.time Linux agent collects the following performance metrics from the systems on which it is installed:
Each set of performance metrics is averaged over an interval of one second.
CPU
The up.time agent uses the sar -urWqR 1 command to compare the system counters during a one-second interval. The statistics returned by the agent are averaged for all CPUs on the system.
| Metric | Explanation | Source |
| % USR | The percentage of time that the processor spends in user mode (a processing mode for applications and subsystems). | /proc/cpuinfo |
| % SYS | The percentage of time that the kernel spends processing system calls. | /proc/cpuinfo |
| % WIO | The amount of waiting time that a runnable process for a device takes to perform an I/O operation. | /proc/cpuinfo |
| % Total | The total amount of User %, System %, and Wait I/O % | /proc/cpuinfo |
| Run Queue Length | The percentage of time that one or more services or processes are waiting to be served by the CPU. | /proc/cpuinfo |
Multi-CPU
The up.time agent uses the sar and mpstat utilities on a Linux system to collect the metrics in the table below from Linux systems with multiple CPUs. The agent averages the statistics from each CPU using the sar -x SELF -I SUM -P ALL -wu 1 command, which compares the system counters during a one-second interval. The statistics that the agent returns are for the entire system, per CPU.
| Metric | Explanation |
| User % | The percentage of CPU user processes that are in use. |
| System % | The percentage of CPU kernel processes that are in use. |
| Wait I/O % | The percentage of time that a process which can be run must wait for a device to perform an I/O operation. |
| SMTX | The number of read or write locks that a thread was not able to acquire on the first attempt, as reported by the mpstat command. |
| XCAL | The number of interprocess cross-calls. In a multi-processor environment, one processor sends cross-calls to another processor to get that processor to do work. Cross-calls can also be used to ensure consistency in virtual memory. Heavy file system activity (such as NFS) can result in a high number of cross-calls. |
| Interrupts | The number of CPU interrupts. |
| Total % | The total amount of User %, System %, and Wait I/O%. |
Memory
The up.time agent uses the free command to collect the Free Memory metric from a Linux system. The rest of the memory related metrics are gathered by the sar -urWqR 1 command which compares the system counters during a one-second interval. The statistics that the agent returns are for the entire system.
| Metric | Explanation | Source |
| Free Memory | The amount of physical memory available to the operating system, system library files, and applications. | /proc/meminfo |
| Cache Hit Rate | How often the system accesses the CPU cache. | /proc/meminfo |
| PageOut per Second | The rate at which pages were written to disk. | /proc/meminfo |
| PageIn per Second | The rate at which pages were read from or written to the disk. | /proc/meminfo |
| PageFree per Second | The number of pages that are freed from memory each second. | /proc/meminfo |
| PageScan per Second | The average number of pages that are scanned each second. | /proc/meminfo |
| Free Swap | The amount of available free swap space, as a percentage of total available free swap space. | /proc/meminfo |
Disk
The up.time agent gathers file system statistics for each file system using the df -lk command. Disk statistics (e.g. %busy, reads per second and writes per second) are output per disk and compared between polling intervals using the iostat -d -x 1 2 command.
| Metric | Explanation | Source |
| Disk (Spindle) Name | The names of each disk on the system. | /proc/diskstats |
| Usage (% Busy) | The percentage of time during which the disk drive is handling read or write requests. | /proc/diskstats |
| Throughput (Blk/s) | The number of read and write operations on the disk that occur each second. | /proc/diskstats |
| Read/Writes/s | The average number of bytes that have been transferred to or from the disk during write or read operations. | /proc/diskstats |
| Average Queue Length | The number of threads that are waiting for processor time. | /proc/diskstats |
| Average Service Time | The average amount of time, in milliseconds, that is required for a request to be carried out. | /proc/diskstats |
| Average Wait Time | The average time, in milliseconds, that a transaction is waiting in a queue. The wait time is directly proportional to the length of the queue. | /proc/diskstats |
Network
The up.time agent uses the netstat -s command to retrieve a combined total of TCP Retransmits for all network interfaces. Other network statistics (e.g. kbps, errors and collisions) are averaged, per interface, using the sar -n DEV -n EDEV 1 command, which compares the system counters during a one-second interval.
| Metric | Explanation | Source |
| In Kbps | The rate, in kilobytes per seconds, at which data is received over a specific network adapter. | /proc/net |
| Out Kbps | The rate, in kilobytes per seconds, at which data is sent over a specific network adapter. | /proc/net |
| In Errors | The number of inbound packets that contained errors, which preventing those packets from being delivered to a higher-layer protocol. | /proc/net |
| Out Errors | The number of outbound packets that could not be transmitted because of errors. | /proc/net |
| Collisions | The number of signals from two separate nodes on the network that have collided. | /proc/net |
| TCP Retransmits | The number of packets that have been re-sent over a network interface. The agent returns a combined total for all interfaces. | /proc/net |
Process
The up.time agent uses the ps -eo command to collect the process information listed in the table below from a Linux system. By default, the agent gathers the top 20 processes and sorts them by the highest CPU usage.
| Metric | Explanation | Source |
| PID | The unique identifier of a specific process. | /proc/stat |
| PPID | The identifier of the process that the process that is currently running. | /proc/stat |
| UID | A value that identifies the current user. | /proc/stat |
| GID | A value that identifies a group of users. | /proc/stat |
| Memory Consumed | The amount of memory that is being used by a process. | /proc/stat |
| RSS | The amount of physical memory that is being used by a process. | /proc/stat |
| CPU % Utilization by Process | The percentage of CPU time that is being used by individual processes. | /proc/stat |
| Memory % Utilization by Process | The amount of physical memory that is being used by individual processes. | /proc/stat |
| Process Start Time | The time at which the process started. | /proc/stat |
| Process Run Time | The time at which the process started. | /proc/stat |
| Number of Processes Running | The total number of processes that are currently running on the system. | /proc/stat |
| Number of Blocked Processes | The total number of processes that are blocking resources. | /proc/stat |
| Number of Waiting Processes | The total number of processes that are waiting to be executed by the CPU. | /proc/stat |
| Execs per Second | The total number of system calls that are executed each second. | /proc/stat |
| Process Creation Rate | The total number of processes that are being spawned over a specified time period. | /proc/stat |
Workload
The up.time agent uses the ps utility to collect workload information from a Linux system. Workload statistics (based on the same 20 processes that were gathered from the Process method) are sorted within up.time's core. The workload processes that the agent gathers include the user/group/process name and their invividual statistics, which can be sorted based on the user's desired graph presentation (e.g. user, group or process name).
| Metric | Explanation | Source |
| Workload by Process | The demand that network and local services are putting on a system, based on the processes that are running. | /proc/load |
| Workload by User | The demand that network and local services are putting on the system, based on the IDs of the users who are logged into a system. | /proc/load |
| Workload by Group | The demand that network and local services are putting on the system, based on the IDs of the user groups that are logged into a system. | /proc/load |
| Workload Top 10 by Process | The 10 processes that are consuming the most CPU resources. | /proc/load |
| Workload Top 10 by User | The 10 processes the are consuming the most CPU resources, based on user ID. | /proc/load |
| Workload Top 10 by Group | The 10 processes the are consuming the most CPU resources, based on group ID. | /proc/load |
User
The up.time agent uses the following commands to collect user statistics from a system:
ps -eolast | head 10(login history for the last 10 users on the system)who(lists who is currently logged into the system)
| Metric | Explanation |
| Login History | The number of times or frequency at which a user has logged into a system during any 30 minute time interval. |
| Sessions | The number of sessions or number of distinct users who are logged into a system during any 30 minute time interval. |