2.5.69 Changes to Kconfig and i386 Makefile to include support for various K7 optimizations
On Wed, May 07, 2003 at 06:34:26PM +0100, Thomas Horsten wrote:
[ick, backlog]
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I made this patch to support the various K7 model-specific optimizations that the later GCC compilers can use.
Please have a look, and pass me any comments.
I don't think this is worth the extra complication. The potential wins (if any) outweigh the confusion to users who might have no clue as to what core they have. Additionally, some gcc's got these options wrong. The athlon4 option was completely wrong for a while for eg.
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I also have the same patch for 2.4, if you are interested it's available on my Linux page on http://www.infowares.com/linux
For 2.4, it's an even worse idea IMO.
Dave
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| Dave Jones. http://www.codemonkey.org.uk | SuSE Labs
Quoted 9 lines · Dave Jones
Quoted 4 lines
I made this patch to support the various K7 model-specific optimizations that the later GCC compilers can use.
Please have a look, and pass me any comments.
I don't think this is worth the extra complication. The potential wins (if any) outweigh the confusion to users who might have no clue as to what core they have. Additionally, some gcc's got these options wrong. The athlon4 option was completely wrong for a while for eg.
I think when GCC supports the different cores, it should be supported by the kernel scripts, the differences between the cores are real enough to have potential optimizations at least in theory (as far as I could see the only difference in GCC 3.2 is whether to use SSE, but that could change in the future).
Maybe it should be renamed "Advanced CPU model selection", or something like that, instead of "K7 Model Selection", but the help IMHO makes it clear enough that you should go with the default if you are not sure and that it will work on any core.
I think it's a fairly simple patch that doesn't break anything, and there are certainly options lurking around in Kconfig that are much more obscure than this :)
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I also have the same patch for 2.4, if you are interested it's available on my Linux page on http://www.infowares.com/linux
For 2.4, it's an even worse idea IMO.
I completely agree that this shouldn't go into the stock 2.4 kernel, that's also why I didn't post it here. It's just on my site as a convenience for those who might want to use the XP specific options etc. in an easy way (like I use it myself).
// Thomas
Quoted 5 lines · Thomas Horsten
I think when GCC supports the different cores, it should be supported by the kernel scripts, the differences between the cores are real enough to have potential optimizations at least in theory (as far as I could see the only difference in GCC 3.2 is whether to use SSE, but that could change in the future).
To use SSE in kernel space, we need to wrap it in kernel_fpu_begin() / kernel_fpu_end() pairs anyway. gcc doesn't (and can't) know this.
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I think it's a fairly simple patch that doesn't break anything
it's non-obvious that it'll break things when people use broken compilers. read what I wrote before, several gcc versions got this horribly wrong. "athlon4" was even tuned for 64bit at one point.
Take away the SSE, take away the broken compiler versions, and you'd be left with something that would hardly show a blip on a benchmark.
Dave