---
title: Determining system capabilities
framework: kernel
role: article
role_heading: Article
path: kernel/1387446-sysctlbyname/determining_system_capabilities
---

# Determining system capabilities

Interrogate the system for processor, cache, and topology information.

## Overview

Overview Obtain information about parameters related to processor availability, cache size, and performance-level characteristics on the system by using the sysctlbyname function. These parameters provide details about your system that can aid in tuning performance. For example, you can obtain the count of the highest-performing processor cores to spawn a worker thread for each core. Or you can determine the size of the L2 cache and the number of processor cores that share it to perform software cache-blocking optimization. Determine processor characteristics The system enables a processor core when it’s powered on and available for thread scheduling. Each logical processor core executes a software thread that the operating system manages. On systems where the number of logical processor cores exceeds the number of physical processor cores, two or more logical processor cores share a physical core through simultaneous multithreading (SMT). The following parameters provide processor availability information about the system on chip (SoC):

Determine system topology The following parameters provide processor core performance-level information. First, determine the number of types of processor cores with hw.nperflevels. Then, for each of the parameters, replace N with a number between 0 and the number of performance levels minus one. Lower values of N indicate higher-performance core types. Querying the following parameters is equivalent to querying the per-performance-level information for the least performant core. For example, hw.l1dcachesize is equivalent to hw.perflevel[N].l1dcachesize, where N is hw.nperflevels minus one.

Determine memory sizes The following parameters provide cache line, memory, and page size information:

## See Also

### Parameters

- [Determining Instruction Set Characteristics](kernel/1387446-sysctlbyname/determining_instruction_set_characteristics.md)