Created attachment 1734937 [details] dmesg 1. Please describe the problem: There is performance dropdown (about 50%) since kernel 5.9.x while scaling video on Intel i3-4130T cpu. 2. What is the Version-Release number of the kernel: 5.9.10 3. Did it work previously in Fedora? If so, what kernel version did the issue *first* appear? Old kernels are available for download at https://koji.fedoraproject.org/koji/packageinfo?packageID=8 : 5.9.7 4. Can you reproduce this issue? If so, please provide the steps to reproduce the issue below: ffmpeg -i fullhd_video.mp4 -benchmark -s 1280x720 -pix_fmt yuv420p -c:v rawvideo -f null - on 5.8.18 -s parameter has almost no influence 5. Does this problem occur with the latest Rawhide kernel? To install the Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by ``sudo dnf update --enablerepo=rawhide kernel``: YES 6. Are you running any modules that not shipped with directly Fedora's kernel?: no 7. Please attach the kernel logs. You can get the complete kernel log for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the issue occurred on a previous boot, use the journalctl ``-b`` flag.
Seems like ffmpeg problem, tried latest git build, it has slightly better results on 5.9.x comparing to 5.8.x. Sorry for bothering.
(In reply to Václav Nováček from comment #1) > Seems like ffmpeg problem, tried latest git build, it has slightly better > results on 5.9.x comparing to 5.8.x. > Sorry for bothering. My mistake, not true, problem still persists, adding -s or -pix_fmt parameter has big influence to the performance on 5.9.x comparing to 5.8.x. Still not sure, where the problem is. The video source is tcp rtsp stream from ipcamera. Decoding file from disk has similar results on 5.9.x and 5.8.x.
Performance problem still persists on kernel 5.10.x What can be the problem? I don't believe it's ffmpeg.
I have tested it on another computer with different hardware (Intel, AMD+nVidia), same problem. It's not related to CPU or GPU. It's the kernel itself.
here are cpu consumptions of the ffmpeg process for comparison kernel 5.8 -s 1280x720 -pix_fmt yuv420p ... about 23% cpu usage of single core kernel 5.9, 5.10 -s 1280x720 -pix_fmt yuv420p ... about 70% cpu usage of single core -s 1280x720 ... about 50% cpu usage of single core only decoding ... about 25% cpu usage of single core it's very simillar on Intel and AMD as well tested on the latest dev build of ffmpeg
It turned out that kernel 5.9+ switched from ondemand to schedutil governor and therefore performance results differ. Switching back to ondemand fixed it.