i686 quirk for AMD Geode
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From: Sven-Haegar Koch on 8 Nov 2009 14:40 On Sun, 8 Nov 2009, Pavel Machek wrote: > On Sun 2009-11-08 18:40:06, Matteo Croce wrote: > > On Sun, Nov 8, 2009 at 6:37 PM, Pavel Machek <pavel(a)ucw.cz> wrote: > > > On Fri 2009-11-06 23:18:06, Matteo Croce wrote: > > >> On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa(a)zytor.com> wrote: > > >> > On 11/06/2009 06:59 AM, Matteo Croce wrote: > > >> >> indeed it has MMX, MMXEXT and CMOV, just lacks the long NOP instruction (NOPL). > > >> > > > >> > MMX and MMXEXT are hardly hallmarks of i686, which leaves only cmov. > > >> > I'm somewhat wondering about the general value of this patch; is i686 > > >> > code really that much faster on Geode that it's worth it? > > >> > > > >> > ? ? ? ?-hpa > > >> > > > >> > -- > > >> > H. Peter Anvin, Intel Open Source Technology Center > > >> > I work for Intel. ?I don't speak on their behalf. > > >> > > > >> > > > >> > > >> yes, I did some test like gzip, bzip2, lame etc and they give more or less > > >> the same results of dhrystone > > >> > > >> root(a)alix:/usr/src# CFLAGS='-march=i586' ./dry.c > > >> Microseconds for one run through Dhrystone: 1.4 > > >> Dhrystones per Second: 740741 > > > ... > > >> root(a)alix:/usr/src# CFLAGS='-march=i686' ./dry.c > > >> Trying 5000000 runs through Dhrystone: > > >> Microseconds for one run through Dhrystone: 1.2 > > >> Dhrystones per Second: 841751 > > > > > > Teach gcc that geodelx exists? No need to break kernel for that... and > > > you probably can gain even bigger gains. But no standard distribution will be made available in a geode special version - not enough machines in the marekt. So I think it is better to be able to use the i686 specific things they already support, like libc6-686 from debian for example. c'ya sven -- The lights are fading out, once more...
From: Pavel Machek on 8 Nov 2009 14:40 On Sun 2009-11-08 20:29:55, Sven-Haegar Koch wrote: > On Sun, 8 Nov 2009, Pavel Machek wrote: > > > On Sun 2009-11-08 18:40:06, Matteo Croce wrote: > > > On Sun, Nov 8, 2009 at 6:37 PM, Pavel Machek <pavel(a)ucw.cz> wrote: > > > > On Fri 2009-11-06 23:18:06, Matteo Croce wrote: > > > >> On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa(a)zytor.com> wrote: > > > >> > On 11/06/2009 06:59 AM, Matteo Croce wrote: > > > >> >> indeed it has MMX, MMXEXT and CMOV, just lacks the long NOP instruction (NOPL). > > > >> > > > > >> > MMX and MMXEXT are hardly hallmarks of i686, which leaves only cmov. > > > >> > I'm somewhat wondering about the general value of this patch; is i686 > > > >> > code really that much faster on Geode that it's worth it? > > > >> > > > > >> > ? ? ? ?-hpa > > > >> > > > > >> > -- > > > >> > H. Peter Anvin, Intel Open Source Technology Center > > > >> > I work for Intel. ?I don't speak on their behalf. > > > >> > > > > >> > > > > >> > > > >> yes, I did some test like gzip, bzip2, lame etc and they give more or less > > > >> the same results of dhrystone > > > >> > > > >> root(a)alix:/usr/src# CFLAGS='-march=i586' ./dry.c > > > >> Microseconds for one run through Dhrystone: � � � �1.4 > > > >> Dhrystones per Second: � � � � � � � � � � � � �740741 > > > > ... > > > >> root(a)alix:/usr/src# CFLAGS='-march=i686' ./dry.c > > > >> Trying 5000000 runs through Dhrystone: > > > >> Microseconds for one run through Dhrystone: � � � �1.2 > > > >> Dhrystones per Second: � � � � � � � � � � � � �841751 > > > > > > > > Teach gcc that geodelx exists? No need to break kernel for that... and > > > > you probably can gain even bigger gains. > > But no standard distribution will be made available in a geode special > version - not enough machines in the marekt. So I think it is better to > be able to use the i686 specific things they already support, like > libc6-686 from debian for example. So hack your distribution to use libc6-686 if you know that it is safe... (that is no NOPL usage there). Still no need to break /proc/cpuinfo. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Matteo Croce on 8 Nov 2009 14:50 On Sun, Nov 8, 2009 at 8:29 PM, Sven-Haegar Koch <haegar(a)sdinet.de> wrote: > On Sun, 8 Nov 2009, Pavel Machek wrote: > >> On Sun 2009-11-08 18:40:06, Matteo Croce wrote: >> > On Sun, Nov 8, 2009 at 6:37 PM, Pavel Machek <pavel(a)ucw.cz> wrote: >> > > On Fri 2009-11-06 23:18:06, Matteo Croce wrote: >> > >> On Fri, Nov 6, 2009 at 5:44 PM, H. Peter Anvin <hpa(a)zytor.com> wrote: >> > >> > On 11/06/2009 06:59 AM, Matteo Croce wrote: >> > >> >> indeed it has MMX, MMXEXT and CMOV, just lacks the long NOP instruction (NOPL). >> > >> > >> > >> > MMX and MMXEXT are hardly hallmarks of i686, which leaves only cmov. >> > >> > I'm somewhat wondering about the general value of this patch; is i686 >> > >> > code really that much faster on Geode that it's worth it? >> > >> > >> > >> > ? ? ? ?-hpa >> > >> > >> > >> > -- >> > >> > H. Peter Anvin, Intel Open Source Technology Center >> > >> > I work for Intel. ?I don't speak on their behalf. >> > >> > >> > >> > >> > >> >> > >> yes, I did some test like gzip, bzip2, lame etc and they give more or less >> > >> the same results of dhrystone >> > >> >> > >> root(a)alix:/usr/src# CFLAGS='-march=i586' ./dry.c >> > >> Microseconds for one run through Dhrystone: � � � �1.4 >> > >> Dhrystones per Second: � � � � � � � � � � � � �740741 >> > > ... >> > >> root(a)alix:/usr/src# CFLAGS='-march=i686' ./dry.c >> > >> Trying 5000000 runs through Dhrystone: >> > >> Microseconds for one run through Dhrystone: � � � �1.2 >> > >> Dhrystones per Second: � � � � � � � � � � � � �841751 >> > > >> > > Teach gcc that geodelx exists? No need to break kernel for that... and >> > > you probably can gain even bigger gains. > > But no standard distribution will be made available in a geode special > version - not enough machines in the marekt. So I think it is better to > be able to use the i686 specific things they already support, like > libc6-686 from debian for example. That's exactly the patch point -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Pavel Machek on 8 Nov 2009 15:00 > >> But no standard distribution will be made available in a geode special > >> version - not enough machines in the marekt. So I think it is better to > >> be able to use the i686 specific things they already support, like > >> libc6-686 from debian for example. > > > > So hack your distribution to use libc6-686 if you know that it is > > safe... (that is no NOPL usage there). Still no need to break > > /proc/cpuinfo. > > Better to be sure that a NOPL whouldn't SIGILL your program, isn't > it? SIGILL is easier to debug than NOPL mysteriously taking 100x time it should, sorry. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Pavel Machek on 8 Nov 2009 15:00
> >> > > Teach gcc that geodelx exists? No need to break kernel for that... and > >> > > you probably can gain even bigger gains. > > > > But no standard distribution will be made available in a geode special > > version - not enough machines in the marekt. So I think it is better to > > be able to use the i686 specific things they already support, like > > libc6-686 from debian for example. > > That's exactly the patch point Not quite. Your cpu is not 686; stop trying to pretend it is. Now, maybe it is good idea to run libc6-686 on it. If you can guarantee it contains no NOPL, fix whatever code is responsible for selecting libc to use libc6-686 to use that. (Bonus points for renaming libc6-686 to something more suitable. libc6-cmov?) Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |