On Fri, 4 May 2012 18:58:59 -0700, Ben Widawsky <ben at bwidawsk.net> wrote:
> I'm seeing about a 5% FPS improvement across various benchmarks on my
> IVB i3. Rumor has it that the higher end parts show even more benefit.
>
> This derives from a patch originally given to me by Bernard. The docs
> are confusing about the definition names (ie. medium really seems like
> max), but it would seem it gives more cache to the GT at the expense of
> uncore. This configuration makes the split most in favor of the GT. I've
> not tried the other IDICOS values.
My IVB system started with an SNBPCR value of 0x1b40. To test the effect of
this patch, I just smashed the value of the reg at runtime:
Results:
x intel_reg_write 0x900c 0x001b40
+ intel_reg_write 0x900c 0x201b40
citybench:
+------------------------------------------------------------------------------+
| xxx + |
| x xxx + + + |
| x xxx + +++ |
| x xxx + + ++++ |
| xx xxxx + + ++++ |
|x xxx x xxxx + + ++++++ ++ |
|xxxxx xxxxxxxx + + + + +*++++ ++ |
|xxxxxxxxx xxxxxxxx x +++++ ++++ +*+++++++ |
|xxxxxxxxx xxxxxxxxxx x ++++++++++ ++**+++++++ + + |
|xxxxxxxxx xxxxxxxxxxxxxx *++++++++++++ ****+*++++++++ + ++++++ +|
| |___________AM_________| |_________A_M_______| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 118 335.779 387.456 354.306 352.63131 12.462796
+ 118 367.324 419.02 386.14 384.47139 10.970918
Difference at 95.0% confidence
31.8401 +/- 2.99585
9.02928% +/- 0.849569%
(Student's t, pooled s = 11.7406)
openarena:
+------------------------------------------------------------------------------+
| + ++ xx xx x x xx |
| + + ++ + + xxxxxxx xxxxx |
| +++ ++++++++++ ++++++ ++ + x xxxxxxxxxxxxxxx xx|
|++ + ++++++++++++++++++++++++++++ + + + x x xxxxxxxxxxxxxxxxxx xx|
| |_________A________| |_____A____| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 65 273.5 292.2 284 283.73385 4.2561822
+ 65 234.8 263.2 249.9 249.6 6.9873323
Difference at 95.0% confidence
-34.1338 +/- 1.989
-12.0302% +/- 0.70101%
nexuiz:
+------------------------------------------------------------------------------+
| + |
| x + + |
| + x x xx *x+ +x |
|+ + + x *x+x xxx + x++ + x+*xxxx+x***x+++*x**+x ++ *+|
| |____|____________AAM____M_____|______| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 33 74.314888 76.177197 75.424764 75.332161 0.48205891
+ 33 73.397254 76.219868 75.584749 75.363209 0.69408523
Using these 3 tests, this patch does not look like a win. Note that OA
is the most CPU-bound of these, while nexuiz is usually on the edge
between being CPU and GPU-bound, and citybench is definitely GPU
limited.
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