Is it possible, that 32-bit kernel with HIGHMEM is faster?

Hello,
I have PC with 2 Gigs of RAM and I was curious if I can get performance gain disabling CONFIG_HIGHMEM and using CONFIG_VMSPLIT_2G_OPT. I have tested performance by running mplayer with some HD trailers (GPU is old Radeon with OSS drivers - only Xv acceleration). From results I see, that kernel with HIGHMEM is slightly faster. I know, I haven't used much memory only by running mplayer alone, but I have expected, that every access to memory will be slower with HIGHMEM. I don't understand, why is HIGHMEM faster, but almost all articles about CONFIG_VMSPLIT_* and CONFIG_PAGE_OFFSET are from year 2006.

CPU is Intel P4 2.80GHz with disabled HT (kernel has not enabled CONFIG_SMP). Memory is 4x 512 MB dual-channel 400MHz CL3. Used kernel was 3.2.1 with CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS.

Diff of config:

Code:

---

-# CONFIG_NOHIGHMEM is not set
-CONFIG_HIGHMEM4G=y
+CONFIG_NOHIGHMEM=y
+# CONFIG_HIGHMEM4G is not set
 # CONFIG_HIGHMEM64G is not set
-CONFIG_PAGE_OFFSET=0xC0000000
-CONFIG_HIGHMEM=y
+# CONFIG_VMSPLIT_3G is not set
+# CONFIG_VMSPLIT_3G_OPT is not set
+# CONFIG_VMSPLIT_2G is not set
+CONFIG_VMSPLIT_2G_OPT=y
+# CONFIG_VMSPLIT_1G is not set
+CONFIG_PAGE_OFFSET=0x78000000

---

Code:

---

$ mplayer -fs -nosound -benchmark

---

Movie (codec)	HIGHMEM (-vo null)	VMSPLIT_2G_OPT (-vo null)	VMSPLIT performance % (-vo null)	HIGHMEM (-vo xv)	VMSPLIT_2G_OPT (-vo xv)	VMSPLIT performance % (-vo xv)
Avatar 1080p (ffh264)	111.479s	114.822s	97.0%	123.826s	126.070s	98.2%
nVidia PureVideo 1080p (wmv9dmo)	165.938s	166.637s	99.6%	181.632s	184.528s	98.4%
Star Trek 11 1080p (wmv9dmo)	69.056s	68.384s	101.0%	78.598s	80.052s	98.2%

This sounds like a good question for Intel and nVidia engineers. I doubt that any of us here have the expertise required to answer your well-put question. In my case, the only rational question is "is it fast enough", and the only rational answer is either "yes" or "no".