Environment:
* ICL GT2 B4 , graphics id 0x8a52
* 5.1.0-rc2-drm-tip : 79df6ae8e7d6fc94965a14e1fa04898954d40316
* https://github.com/intel/media-driver/ : 8773ef5
* https://github.com/intel/gmmlib : e65dff3 (includes GMM MOCS table fix)
* https://github.com/Intel-Media-SDK/MediaSDK : 2c780ea

We're using the following script to fix CPU/GPU frequency on ICL:
#!/bin/bash
set -ex
cpupower frequency-set --governor performance
cpupower frequency-set --min 1000000
cpupower frequency-set --max 1000000
echo 400 > /sys/class/drm/card0/gt_min_freq_mhz
echo 400 > /sys/class/drm/card0/gt_max_freq_mhz
echo 400 > /sys/class/drm/card0/gt_boost_freq_mhz 

However media workloads produce very different performance from run to run.

perf stat -a -e i915/bcs0-busy/,i915/rcs0-busy/,i915/vcs0-busy/,i915/vecs0-busy/,i915/actual-frequency/,i915/requested-frequency/ ./sample_encode h264 -i input.yuv -qpi 26 -qpp 26 -qpb 26   -async 1 -hw  -w 720 -h 480 -n 300 -r 1 -vaapi -g 100
File output is disabled as -o option isn't specified
libva info: VA-API version 1.5.0
libva info: va_getDriverName() returns 0
libva info: User requested driver 'iHD'
libva info: Trying to open /opt/intel/mediasdk/lib64/iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_4
libva info: va_openDriver() returns 0
Encoding Sample Version 8.3.26.

Input file format   YUV420
Output video        AVC 
Source picture:
    Resolution  720x480
    Crop X,Y,W,H    0,0,720,480
Destination picture:
    Resolution  720x480
    Crop X,Y,W,H    0,0,720,480
Frame rate  30.00
Bit rate(Kbps)  2503
Gop size    100
Ref dist    1
Ref number  0
Idr Interval    0
Target usage    balanced
Memory type vaapi
Media SDK impl      hw
Media SDK version   1.29

Processing started

Processing finished

 Performance counter stats for 'system wide':

                 0 ns   i915/bcs0-busy/                                             
     4,078,817,486 ns   i915/rcs0-busy/                                             
       748,226,339 ns   i915/vcs0-busy/                                             
                 0 ns   i915/vecs0-busy/                                            
               791 MHz  i915/actual-frequency/                                      
             3,137 MHz  i915/requested-frequency/                                   

       7.912914519 seconds time elapsed

It looks like frequency is not actually fixed while the same approach works fine on SKL.