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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 ...
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- 02-04-2012 #1
- Join Date
- May 2009
Is it possible, that 32-bit kernel with HIGHMEM is faster?
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:
-# 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=0x78000000Code:
$ 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%
- 02-09-2012 #2
- Join Date
- Apr 2009
- I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
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".
Just remember, Semper Gumbi - always be flexible!