Fedora performance and Intel i915?

Jeffrey Ross via users <users@xxxxxxxxxxxxxxxxxxxxxxx> · Thu, 10 Mar 2022 14:32:43 -0500



    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

  
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