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Performance Counters for Linux Wiki

This is the wiki page for the perfcounters subsystem in Linux.

Performance counters are special hardware registers available on most modern CPUs. These registers count the number of certain types of hw events: such as instructions executed, cache-misses suffered, or branches mispredicted - without slowing down the kernel or applications. These registers can also trigger interrupts when a threshold number of events have passed - and can thus be used to profile the code that runs on that CPU.

The Linux Performance Counter subsystem provides rich abstractions over these hardware capabilities. It provides per task, per CPU and per-workload counters, counter groups, and it provides sampling capabilities on top of those - and more.

It also provides abstraction for 'software events' - such as minor/major page faults, task migrations, task context-switches and tracepoints.

There is a new tool ('perf') that makes full use of this new kernel subsystem. It can be used to optimize, validate and measure applications, workloads or the full system.

'perf' is hosted in the upstream kernel repository and can be found under: tools/perf/

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