[Bug 314928] Re: [i915GM] MTRR entry missing since jaunty - is this intentional?

Conn connogriofa at gmail.com
Tue Apr 14 03:07:17 UTC 2009


I can confirm this on a DELL Inspiron 510m laptop & Jaunty, with all the
latest updates. The most notable problem I experience is stuttering
video through Totem (using the standard GStreamer backend, Xv output)
and other media players.

Relevant lspci -vvnn output:

00:02.0 VGA compatible controller [0300]: Intel Corporation 82852/855GM Integrated Graphics Device [8086:3582] (rev 02)
	Subsystem: Dell Device [1028:0164]
	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx+
	Latency: 0
	Interrupt: pin A routed to IRQ 11
	Region 0: Memory at f0000000 (32-bit, prefetchable) [size=128M]
	Region 1: Memory at faf80000 (32-bit, non-prefetchable) [size=512K]
	Region 2: I/O ports at c000 [size=8]
	Capabilities: <access denied>
	Kernel modules: intelfb

Current MTRR setup:

conn at inspiron:~$ cat /proc/mtrr 
reg00: base=0x000000000 (    0MB), size=  512MB, count=1: write-back
reg01: base=0x020000000 (  512MB), size=  256MB, count=1: write-back
reg02: base=0x02ff00000 (  767MB), size=    1MB, count=1: uncachable
reg03: base=0x0feda0000 ( 4077MB), size=  128KB, count=1: write-through

The fix:
sudo -s
echo "base=0xF0000000 size=0x08000000 type=write-combining" >| /proc/mtrr

Enabling write combining allows Totem to play 720p content with
absolutely no stuttering (compared to low-resolution content stuttering
without the fix). I can't say that I notice a huge increase in 3D
performance, however.  I won't bother to report glxgears scores, it's
not an accurate tool to measure performance.

-- 
[i915GM] MTRR entry missing since jaunty - is this intentional?
https://bugs.launchpad.net/bugs/314928
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