Performance levels and performance determinism#
AMD GPUs expose power management controls through the AMD SMI library and CLI
tool. This document covers performance levels (--perf-level) and
performance determinism (--perf-determinism): what they do, how they work
in the driver stack, and which GPUs support them.
Performance levels#
What is a performance level?#
A performance level controls the PowerPlay dynamic power management (DPM) policy on the GPU. PowerPlay automatically adjusts clock frequencies (GFXCLK/SCLK and UCLK/MCLK) based on workload demand. Setting a performance level overrides this automatic behavior with a specific policy.
The request flows through the stack as:
AMD SMI (user space) calls
amdsmi_set_gpu_perf_level().The amdgpu kernel driver writes the level to the
power_dpm_force_performance_levelsysfs file.The driver sends a PMFW (Power Management Firmware) message to the SMU (System Management Unit).
PMFW enforces the clock and power behavior on the hardware.
Available levels#
Level |
Enum value |
Description |
|---|---|---|
|
|
Default. PowerPlay dynamically adjusts clocks based on workload demand. |
|
|
Forces clocks to minimum regardless of workload. |
|
|
Forces clocks to maximum regardless of workload. |
|
|
Enables manual control of GFXCLK (SCLK) frequency ranges. Required before setting clock levels or overdrive. |
|
|
Stable power state with standard profiling clocks. |
|
|
Stable power state with peak clocks. |
|
|
Stable power state with minimum memory clock. |
|
|
Stable power state with minimum system clock. |
|
|
Performance determinism state. Set automatically when determinism mode is enabled. |
Note
MANUAL mode is a prerequisite for setting individual clock frequency levels
(amd-smi set --clk-level) or clock ranges (amd-smi set --clk-limit).
Setting the level back to AUTO restores dynamic power management.
How the driver handles performance levels#
The kernel driver (for example,
smu_v13_0.c)
translates each level into PMFW messages. The sysfs strings written by the
driver are: auto, low, high, manual, profile_standard,
profile_peak, profile_min_mclk, profile_min_sclk, and
perf_determinism.
Since AMD SMI supports multiple ASICs, a given ASIC may only support a subset of these levels. If the ASIC firmware does not support the requested level, the call returns an error.
Performance determinism#
What is performance determinism?#
Performance determinism is a specialized mode that delivers consistent, predictable performance across multiple GPUs. It enforces a user-defined SoftMax limit on the GFXCLK frequency, preventing the GFXCLK PLL (Phase-Locked Loop) from stretching when running the same workload on different GPUs.
Why it matters#
In multi-GPU workloads (for example, distributed LLM inference or training), individual GPUs can exhibit clock frequency variations due to silicon variation, thermal conditions, and voltage/frequency curve differences. This causes:
Synchronization stalls – faster GPUs idle while waiting for slower ones.
Unpredictable latency – job completion time is driven by the slowest GPU.
Benchmarking inaccuracy – results vary between runs.
Performance determinism eliminates this by capping all GPUs at the same maximum GFXCLK frequency.
How it works#
When you enable performance determinism via
amdsmi_set_gpu_perf_determinism_mode() or amd-smi set --perf-determinism <SCLKMAX>:
The GPU performance level is set to
DETERMINISM.A SoftMax limit is written to the GPU’s overdrive/voltage control interface, setting the maximum GFXCLK frequency to the user-specified value (in MHz).
The change is committed to hardware.
Internally the driver performs:
1. Writes "perf_determinism" to power_dpm_force_performance_level
2. Writes "s 1 <clkvalue>" to pp_od_clk_voltage (sets max SCLK)
3. Writes "c" to pp_od_clk_voltage (commits the change)
The GPU will not exceed the specified frequency. The clock can still scale down under light loads.
GPU support#
Important
Support for performance levels and determinism is ASIC-specific and depends on PMFW capabilities. AMD SMI forwards requests to the kernel driver, which sends them to PMFW. If the firmware does not support a feature, the operation returns an error.
Feature |
MI200 |
MI300 |
MI350 |
RDNA 3 |
RDNA 4 |
|---|---|---|---|---|---|
|
✅ |
✅ |
✅ |
✅ |
✅ |
|
✅ |
✅ |
✅ |
✅ |
❓ |
|
✅ |
✅ |
✅ |
✅ |
❓ |
|
✅ |
✅ |
✅ |
✅ |
❓ |
|
✅ |
✅ |
❓ |
✅ |
❓ |
|
✅ |
⚠️ |
❌ |
✅ |
❓ |
Legend: ✅ Supported ⚠️ Limited / ASIC-dependent ❌ Not supported ❓ Unconfirmed
Notes on specific GPU families:
MI200 (Aldebaran) – Full support for all performance levels and determinism.
MI300 (Aqua Vanjaram) – Performance determinism support depends on the PMFW version. Verify with
amd-smi metric --perf-levelafter setting.MI350 – Performance determinism is defeatured. CSC (Clock Stretching Compensation) is intended to address the variability use case that determinism previously covered.
RDNA 3 (Navi 3x) – Full support for performance levels and determinism.
RDNA 4 (Navi 4x) – Depends on PMFW capabilities for the specific ASIC.
From concept to action#
amdsmi_get_gpu_perf_level()– Query the current DPM performance level.amdsmi_set_gpu_perf_level()– Set the PowerPlay performance level.amdsmi_set_gpu_perf_determinism_mode()– Enable performance determinism with a GFXCLK SoftMax (in MHz).
See Clock, Power, and Performance Control for the full API reference.
amdsmi_get_gpu_perf_level – Query current performance level.
amdsmi_set_gpu_perf_level – Set performance level.
amdsmi_set_gpu_perf_determinism_mode – Enable performance determinism.
See amd-smi set --help and
amd-smi reset --help for all
options.
# Query current performance level
amd-smi metric --perf-level
# Set performance level
amd-smi set --perf-level HIGH
# Enable performance determinism with GFXCLK capped at 1900 MHz
amd-smi set --perf-determinism 1900
# Disable performance determinism
amd-smi reset --perf-determinism
# Reset to automatic
amd-smi set --perf-level AUTO