I've been chasing some performance issues on a recently reinstalled Fedora system and I think I've identified the problem along with what maybe an incomplete or not fully optimized solution.

The problem started when I had upgraded to Fedora 35 the upgrade went south with the booting of the OS, grub for whatever reason reverted to trying to boot a very old kernel that didn't exist.  I figured the easiest and fastest way was to simply reinstall the OS, retaining my /home partition.  The re-installation went fine however performance SUCKED, it so so bad that using firefox, thunderbird, and chrome I could type faster than the system can display characters on the screen.

Apparently quite some time ago I had put in some options into grub that enabled optimizations with the i915 graphics chipset and had forgotten about it.  So after a lot of digging I have added to the GRUB_CMDLINE_LINUX line in the /etc/default/grub file:
 
      i915.enable_rc6=7 i915.enable_fbc=1 i915.lvds_downclock=1 i915.semaphores=1

This seems to have given me a dramatic boost in system performance, and I no longer have lag when I'm typing, the system is loading web pages etc a whole lot faster, and CPU usage is way down.

Now I'm not confident I have the best options enabled for my system with its i915 chipset and I'm also not sure I have added it in the correct location.

The system is an older laptop, Lenovo T440P (4th gen i7)

hwinfo identifies the i915 as the following:
33: PCI 02.0: 0300 VGA compatible controller (VGA)
  [Created at pci.386]
  Unique ID: _Znp.rz2n9XAjpu9
  SysFS ID: /devices/pci0000:00/0000:00:02.0
  SysFS BusID: 0000:00:02.0
  Hardware Class: graphics card
  Model: "Intel 4th Gen Core Processor Integrated Graphics Controller"
  Vendor: pci 0x8086 "Intel Corporation"
  Device: pci 0x0416 "4th Gen Core Processor Integrated Graphics Controller"
  SubVendor: pci 0x17aa "Lenovo"
  SubDevice: pci 0x221d
  Revision: 0x06
  Driver: "i915"
  Driver Modules: "i915"
  Memory Range: 0xf3000000-0xf33fffff (rw,non-prefetchable)
  Memory Range: 0xc0000000-0xdfffffff (ro,non-prefetchable)
  I/O Ports: 0x4000-0x403f (rw)
  Memory Range: 0x000c0000-0x000dffff (rw,non-prefetchable,disabled)
  IRQ: 35 (10229876 events)
  Module Alias: "pci:v00008086d00000416sv000017AAsd0000221Dbc03sc00i00"
  Driver Info #0:
    Driver Status: i915 is active
    Driver Activation Cmd: "modprobe i915"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
I also see the following in the kernel log (as pulled from hwinfo)
  <3>[   38.067230] i915 0000:00:02.0: [drm] *ERROR* mstb 00000000b560c211 port 3: DPCD read on addr 0x4b0 for 1 bytes NAKed
Any suggestions on tweaking the i915 configuration would be appreciated