CONFIG_UCLAMP_BUCKETS_COUNT: Number of supported utilization clamp buckets

General informations

The Linux kernel configuration item CONFIG_UCLAMP_BUCKETS_COUNT:

• prompt: Number of supported utilization clamp buckets
• type: int
• depends on: CONFIG_UCLAMP_TASK
• defined in init/Kconfig
• found in Linux kernels: 5.3–5.19, 6.0–6.8, 6.9-rc+HEAD

Help text

Defines the number of clamp buckets to use. The range of each bucket will be SCHED_CAPACITY_SCALE/UCLAMP_BUCKETS_COUNT. The higher the number of clamp buckets the finer their granularity and the higher the precision of clamping aggregation and tracking at run-time.

For example, with the minimum configuration value we will have 5 clamp buckets tracking 20% utilization each. A 25% boosted tasks will be refcounted in the [20..39]% bucket and will set the bucket clamp effective value to 25%. If a second 30% boosted task should be co-scheduled on the same CPU, that task will be refcounted in the same bucket of the first task and it will boost the bucket clamp effective value to 30%. The clamp effective value of a bucket is reset to its nominal value (20% in the example above) when there are no more tasks refcounted in that bucket.

An additional boost/capping margin can be added to some tasks. In the example above the 25% task will be boosted to 30% until it exits the CPU. If that should be considered not acceptable on certain systems, it's always possible to reduce the margin by increasing the number of clamp buckets to trade off used memory for run-time tracking precision.

If in doubt, use the default value.

Hardware

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This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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